What does an allergist do for food allergies
If you ponder you or your kid may own a food allergy, it’s extremely significant to enquire for a professional diagnosis from your GP.
They can then refer you to an allergy clinic if appropriate.
Many parents mistakenly assume their child has a food allergy when their symptoms are actually caused by a completely different condition.
Commercial allergy testing kits are available, but using them isn’t recommended. Numerous kits are based on unsound scientific principles. Even if they are dependable, you should own the results looked at by a health professional.
Read more about diagnosing food allergies.
What is food intolerance?
A food intolerance isn’t the same as a food allergy.
People with food intolerance may own symptoms such as diarrhoea, bloating and stomach cramps.
This may be caused by difficulties digesting certain substances, such as lactose. However, no allergic reaction takes place.
Important differences between a food allergy and a food intolerance include:
- you need to eat a larger quantity of food to trigger an intolerance than an allergy
- the symptoms of a food intolerance generally happen several hours after eating the food
- a food intolerance is never life threatening, unlike an allergy
Read more about food intolerance.
Sheet final reviewed: 15 April
Next review due: 15 April
en español¿En qué se diferencia una alergia alimentaria de una intolerancia alimentaria?
What is the difference between food allergies and food intolerances?
Food allergies and food intolerances (or sensitivities) can own similar symptoms, but are extremely diverse conditions:
A food intolerance means either the body cannot properly digest the food that is eaten, or that a specific food might irritate the digestive system.
Symptoms of food intolerance can include nausea, gas, cramps, abdominal pain, diarrhea, irritability, nervousness, or headaches.
A food allergy happens when the body’s immune system, which normally fights infections, sees the food as an invader. This leads to an allergic reaction — a response from the immune system in which chemicals love histamine are released in the body. The reaction can cause symptoms love breathing problems, throat tightness, hoarseness, coughing, vomiting, abdominal pain, hives, swelling, or a drop in blood pressure.
Even if previous reactions own been mild, someone with a food allergy is always at risk of the next reaction being life-threatening.
Eating a microscopic quantity of the food, or sometimes even touching or inhaling it, could lead to anaphylaxis. So anyone with a food allergy must avoid the problem food(s) entirely and always carry emergency injectable epinephrine.
Many people with food sensitivities, on the other hand, can ingest a little quantity of the bothersome food without a problem.
The primary way to manage a food allergy is to avoid consuming the food that causes you problems. Carefully check ingredient labels of food products, and study whether what you need to avoid is known by other names.
The Food Allergy Labeling and Consumer Protection Act of (FALCPA) mandates that manufacturers of packaged foods produced in the United States identify, in simple, clear language, the presence of any of the eight most common food allergens — milk, egg, wheat, soy, peanut, tree nut, fish and crustacean shellfish — in their products.
The presence of the allergen must be stated even if it is only an incidental ingredient, as in an additive or flavoring.
Some goods also may be labeled with precautionary statements, such as “may contain,” “might contain,” “made on shared equipment,” “made in a shared facility” or some other indication of potential allergen contamination. There are no laws or regulations requiring those advisory warnings and no standards that define what they mean. If you own questions about what foods are safe for you to eat, talk with your allergist.
Be advised that the FALCPA labeling requirements do not apply to items regulated by the U.S. Department of Agriculture (meat, poultry and certain egg products) and those regulated by the Alcohol and Tobacco Tax and Trade Bureau (distilled spirits, wine and beer). The law also does not apply to cosmetics, shampoos and other health and beauty aids, some of which may contain tree nut extracts or wheat proteins.
Avoiding an allergen is easier said than done. While labeling has helped make this process a bit easier, some foods are so common that avoiding them is daunting.
A dietitian or a nutritionist may be capable to assist. These food experts will offer tips for avoiding the foods that trigger your allergies and will ensure that even if you exclude certain foods from your diet, you still will be getting every the nutrients you need. Special cookbooks and support groups, either in person or online, for patients with specific allergies can also provide useful information.
Many people with food allergies wonder whether their condition is permanent. There is no definitive answer. Allergies to milk, eggs, wheat and soy may vanish over time, while allergies to peanuts, tree nuts, fish and shellfish tend to be lifelong.
Managing food allergies in children
No parent wants to see their kid suffer.
Since fatal and near-fatal food allergy reactions can happen at school or other places exterior the home, parents of a kid with food allergies need to make certain that their child’s school has a written emergency action plan. The plan should provide instructions on preventing, recognizing and managing food allergies and should be available in the school and during activities such as sporting events and field trips. If your kid has been prescribed an auto-injector, be certain that you and those responsible for supervising your kid understand how to use it.
In November , President Barack Obama signed into law the School Access to Emergency Epinephrine Act (PL ), which encourages states to adopt laws requiring schools to own epinephrine auto-injectors on hand.
As of tardy , dozens of states had passed laws that either require schools to own a supply of epinephrine auto-injectors for general use or permit school districts the option of providing a supply of epinephrine. Numerous of these laws are new, and it is uncertain how well they are being implemented. As a result, ACAAI still recommends that providers caring for food-allergic children in states with such laws maintain at least two units of epinephrine per allergic kid attending the school.
Symptoms caused by a food allergy can range from mild to life-threatening; the severity of each reaction is unpredictable.
People who own previously experienced only mild symptoms may suddenly experience a life-threatening reaction called anaphylaxis, which can, among other things, impair breathing and cause a sudden drop in blood pressure. This is why allergists do not love to classify someone as “mildly” or “severely” food allergic — there is just no way to tell what may happen with the next reaction. In the U.S., food allergy is the leading cause of anaphylaxis exterior the hospital setting.
Epinephrine (adrenaline) is the first-line treatment for anaphylaxis, which results when exposure to an allergen triggers a flood of chemicals that can send your body into shock.
Anaphylaxis can happen within seconds or minutes of exposure to the allergen, can worsen quickly and can be fatal.
Once you’ve been diagnosed with a food allergy, your allergist should prescribe an epinephrine auto-injector and teach you how to use it. You should also be given a written treatment plan describing what medications you’ve been prescribed and when they should be used. Check the expiration date of your auto-injector, note the expiration date on your calendar and enquire your pharmacy about reminder services for prescription renewals.
Anyone with a food allergy should always own his or her auto-injector shut at hand.
Be certain to own two doses available, as the severe reaction can recur in about 20 percent of individuals. There are no data to assist predict who may need a second dose of epinephrine, so this recommendation applies to every patients with a food allergy.
Use epinephrine immediately if you experience severe symptoms such as shortness of breath, repetitive coughing, feeble pulse, hives, tightness in your throat, trouble breathing or swallowing, or a combination of symptoms from diverse body areas, such as hives, rashes or swelling on the skin coupled with vomiting, diarrhea or abdominal pain.
Repeated doses may be necessary. You should call for an ambulance (or own someone nearby do so) and inform the dispatcher that epinephrine was istered and more may be needed. You should be taken to the emergency room; policies for monitoring patients who own been given epinephrine vary by hospital.
If you are uncertain whether a reaction warrants epinephrine, use it correct away; the benefits of epinephrine far outweigh the risk that a dose may not own been necessary.
Common side effects of epinephrine may include anxiety, restlessness, dizziness and shakiness.
In extremely rare instances, the medication can lead to abnormal heart rate or rhythm, heart attack, a sharp increase in blood pressure and fluid buildup in the lungs. If you own certain pre-existing conditions, such as heart disease or diabetes, you may be at a higher risk for adverse effects from epinephrine. Still, epinephrine is considered extremely safe and is the most effective medicine to treat severe allergic reactions.
Other medications may be prescribed to treat symptoms of a food allergy, but it is significant to note that there is no substitute for epinephrine: It is the only medication that can reverse the life-threatening symptoms of anaphylaxis.
Be additional careful when eating in restaurants.
Waiters (and sometimes the kitchen staff) may not always know the ingredients of every dish on the menu.
Depending on your sensitivity, even just walking into a kitchen or a restaurant can cause an allergic reaction.
Consider using a “chef card” — available through numerous websites — that identifies your allergy and what you cannot eat. Always tell your servers about your allergies and enquire to speak to the chef, if possible. Stress the need for preparation surfaces, pans, pots and utensils that haven’t been contaminated by your allergen, and clarify with the restaurant staff what dishes on the menu are safe for you.
Can food allergies be prevented?
In , the American Academy of Pediatrics published a study which supported research suggesting that feeding solid foods to extremely young babies could promote allergies.
It recommends against introducing solid foods tobabies younger than 17 weeks. It also suggests exclusively breast-feeding “for as endless as possible,” but stops short of endorsing earlier research supporting six months of exclusive breast-feeding.
Research on the benefits of feeding hypoallergenic formulas to high-risk children – those born into families with a strong history of allergic diseases – is mixed.
In the case of peanut allergy, the National Institute for Allergy and Infectious Disease (NIAID) issued new updated guidelines in in order to define high, moderate and low-risk infants for developing peanut allergy.
The guidelines also address how to proceed with introduction based on risk.
The updated guidelines are a breakthrough for the prevention of peanut allergy. Peanut allergy has become much more prevalent in recent years, and there is now a roadmap to prevent numerous new cases.
According to the new guidelines, an baby at high risk of developing peanut allergy is one with severe eczema and/or egg allergy. The guidelines recommend introduction of peanut-containing foods as early as months for high-risk infants who own already started solid foods, after determining that it is safe to do so.
Parents should know that most infants are either moderate- or low-risk for developing peanut allergies, and most can own peanut-containing foods introduced at home. Whole peanuts should never be given to infants because they are a choking hazard.
If your kid has no factors to be at high risk, the best way to introduce peanuts is to make certain first of every your kid is healthy – they don’t own a freezing, fever or anything else. Make certain it’s not the first food you’ve introduced to them.
Ruchi Gupta, MD, ACAAI member
Clinical studies are ongoing in food allergy to assist develop tolerances to specific foods.
Askyour board-certified allergistif you or your kid may be a candidate for one of these studies.
Alessandro Fiocchi, MD and Vincenzo Fierro, MD
The Bambino Gesù Children’s Research Hospital
Rome, Holy See
Definition and Classification
The classification of allergic and hypersensitivity diseases was established by the European Academy of Allergy and Clinical Immunology (EAACI) and the World Allergy Organization (WAO) in (1).
The definitions and concepts of allergic and hypersensitivity conditions beyond the allergy community own often created misunderstanding (2). For an optimal clarification:
- “hypersensitivity” is defined as “conditions clinically resembling allergy that cause objectively reproducible symptoms or signs, initiated by exposure to a defined stimulus at a dose tolerated by normal subjects”, and
- the term “atopy” is used when individuals own an IgE sensitization as documented by IgE antibodies in serum or by a positive skin prick test;
- “allergy” is defined “a hypersensitivity reaction initiated by proven or strongly suspected immunologic mechanisms”.
Based on these definitions, a correct diagnosis of allergic disease must adhere to the following conditions:
a) Compatible clinical history; and
b) Positivity to in vivo and/or in vitro tests to prove underlying mechanism and etiology.
The tests alone cannot be used because numerous people are sensitized (positive results to in vivo and/or in vitro tests), but not allergic (no reactions).
Specifically for ‘food allergy’, this term is used when a causal relationship (ideally, with a specific immunological mechanism) has been defined.
There are three wide groups of immune reactions: IgE-mediated, non-IgE-mediated and mixed. The IgE-mediated reactions are generally divided into immediate-onset reactions (arising up to 2 hours from the food ingestion) and immediate plus late-phase (in which the immediate onset symptoms are followed by prolonged or ongoing symptoms). Non-IgE-mediated reactions, which are poorly defined both clinically and scientifically, are believed to be generally T-cell-mediated. They are typically delayed in onset, and happen 4 to 28 hours after ingestion of the offending food(s). Mixed IgE and non-IgE mediated reaction are conditions associated with food allergy involving both IgE- and non-IgE-mediated mechanisms (3).
A series of adverse reactions to foods do not involve an immune response and are not considered food allergies (4).
These include metabolic disorders (for instance, lactose and alcohol intolerance), responses to pharmacologically athletic food components, as caffeine, theobromine in chocolate or tyramine in fermented cheeses, or toxic reactions. Toxic reactions to food can happen in any patient, if a sufficient quantity of the food is ingested; they are due to toxins in the food, e.g., to histamine in scombroid fish or bacterial toxins in food.
While sometimes these, and other presumed food allergic reactions, are defined “food intolerances”, this term should not be used to define an allergic reaction (5).
Host factors such as lactase deficiency, which are associated with lactose intolerance, or idiosyncratic responses may be responsible for other non-allergic reactions to foods.
Underlying Mechanisms of Food Allergy
Typical food allergies are IgE-mediated, but several reactions involve diverse immunologic mechanisms. These food allergies are defined as non–IgE-mediated or mixed IgE- and non–IgE-mediated.
The symptoms of IgE-mediated, non-IgE–mediated, and mixed IgE- and non–IgE-mediated food allergy are presented in Table 13.
IgE-mediated symptoms develop within minutes to hours of ingesting the food, non–IgE-mediated and mixed IgE- and non–IgE-mediated food allergies present with their symptoms several hours after the ingestion of the food.
All these manifestations derive from a failure to develop or a breakdown of food tolerance, resulting in excessive production of food-specific IgE antibodies or in altered cellular events, leading to allergic reactions. Environmental influences and genetic factors of the host underlie the immunopathogenesis of food allergy and its manifestations.
Some clinical studies own revised our understanding of the cause of food allergy. For example, functional genetic variants in the IL receptor b1, Toll-like receptor 9, and thymic stromal lymphopoietin genes and even IL-4 gene polymorphism own been associated with an increased risk of food sensitization (6). In the future, the elucidation of the gene-environment interactions will be crucial for understanding the food allergy pathogenesis. Microbiome, i.e., -omic, studies are an emerging field of interest to define allergy pathogenesis and, in a not too distant future, the microbiome could offer novel therapeutic possibilities (7).
Food allergy is described as an increasing disease over time.
It is generally accepted that food allergy affects approximately % of the general population, but the spread of prevalence data is wide, ranging from 1% to 10%. Precise determination of the prevalence is still one of the major problems with food allergy, considering that numerous factors influence the reported prevalence of food allergy. The varied factors include differing criteria for making food allergy diagnosis, study methodologies, geographic variation, ages, and dietary exposures to name a few.
In European birth cohorts, the incidence ranges from % (United Kingdom) to % (Greece) (8).
The most common foods, eaten separately or included as an ingredient, even in trace amounts (hidden food), that elicit hypersensitivity reactions are milk, egg, wheat, fish, and nuts.
Despite the fact that up to % of newborn during the first years of life are diagnosed as allergic to cow's milk, recent European prevalence data repair the prevalence of cow’s milk allergy (CMA) to % (9).
Within the EuroPrevall birth cohort, the mean adjusted incidence of hen’s egg allergy was % (10), while the Australian Healthnuts study reports a prevalence of 9% (11).
The prevalence of peanut allergy among children in the United Kingdom, North America, and Australia has been reported doubled in 10 years and is approximately %, %, and % respectively.
Fish allergy prevalence ranges from 0% to 7% and the prevalence of shellfish allergy from 0% to %, depending on the method used for diagnosis.
The only study using food challenges reports a prevalence of fish allergy of 0% — % and a prevalence of shellfish allergy ranging between 0% and %. Fish allergy seems more frequent in Asia (12) than in Western countries (13).
Epidemiological studies reveal that among food-allergic infants, approximately 80% will reach tolerance by the fifth birthday, but 35% of them may eventually develop hypersensitivity to other foods. Those with the highest IgE levels, with the most serious clinical manifestations (anaphylaxis and asthma), and with the wider co-sensitizations are less likely to overgrowth their food allergy. The natural history of food allergy also depends on the specific food sensitization, with children allergic to milk and egg displaying a better prognosis than those allergic to peanuts, tree nuts and fish(14).
Cross-Reactivity and Food Allergens
Component Resolved Diagnosis (CRD) elucidated the link between a severe allergy to pollen and the increase of oral allergy syndrome (OAS), exercise induced asthma and anaphylaxis when eating certain foods.
Such reactions are due to cross-reactive allergens as pathogenesis related (PR), profilins, or lipid transfer proteins (LTP). These proteins are ubiquitous in pollens, plants, fruits and food. Individuals sensitive to home dust mites own been reported with oral allergy syndrome following ingestion of shellfish(15). Children with CMA may react to beef in up to 20% of cases, to goat’s milk in 98%, and to donkey milk in 20% of cases(16).
IgE-Mediated Food-Related Disorders
Acute urticaria and angioedema are the most frequent manifestation of food allergy.
The onset of symptoms may be rapid, within minutes, following the ingestion of the offending food. Foods most often implicated include milk, fish, vegetables and fruits. In atopic dermatitis, also a frequent symptom of food allergy, immediate reactions can be followed by tardy cutaneous reactions.
Symptoms caused by immediate sensitivity in the gastrointestinal tract typically develop within minutes to 2 hours of ingesting the offending food.
Symptoms can include lip, tongue and palatal pruritus and swelling, laryngeal oedema, nausea, abdominal cramping, vomiting and diarrhoea. Severe reactions can result in most or every symptoms associated with anaphylaxis.
Oral allergy syndrome (OAS), a form of contact urticaria confined to the lips and oropharynx, most commonly occurs in pollen-allergic patients. Symptoms include oropharyngeal itching, with or without facial angioedema, and/or tingling of the lips, tongue, palate and throat.
Allergic rhinoconjunctivitis and asthma can happen following food challenge testing, but respiratory symptoms from food allergy in the absence of skin or gastrointestinal manifestations are rare.
When respiratory symptoms happen following food challenge, both early- and late-phase IgE-mediated mechanisms are probably involved.
Systemic reaction: Anaphylaxis
Anaphylaxis is an explosive systemic reaction. About 50% of anaphylaxis reactions are due to food allergy. It occurs within few minutes to hours after food ingestion(17). Ninety per cent of patients experience skin (urticaria, angioedema) plus respiratory symptoms such as asthma, rhinitis or conjunctivitis; in 30% of the cases, they also develop gastrointestinal symptoms or hypotension, and shock and cardiac arrhythmias may happen.
Every of this is caused by the massive release of mediators from mast cells and basophils.
A form of anaphylaxis associated to food is the exercise-induced food-dependent anaphylaxis, occurring, generally, hours after ingestion of a food to which the individual is allergic. Food or exercise alone will not cause this reaction. Risk factors for food-induced anaphylaxis include asthma and previous allergic reactions to the causative food.
Table 1. Specific Food-Induced Allergic Conditions3
Non-IgE-Mediated Food Allergic Disorders
Food allergy is also linked to manifestations of delayed hypersensitivity, partially IgE-mediated and partially non-IgE-mediated.
It is implicated in Eosinophilic Esophagitis, Eosinophilic gastritis and gastroenteritis, food protein-induced enterocolitis syndrome, and allergic proctocolitis.
Food protein –induced enterocolitis syndrome (FPIES)
Primarily affects infants. In chronic forms, it presents as emesis, diarrhea, poor growth, and, in severe cases, with starvation and lethargy. In acute forms, or after re-istration of restricted foods, it may determine emesis, diarrhea, and hypotension, starting two hours following ingestion. Diarrhea may be bloody and may result in dehydration, especially in early infancy. It has been associated frequently to ingestion of cow's milk, soy, oat, wheat, and/or rice.
Skin prick test to the suspected foods are generally negative, but IgE-mediated food allergy may be associated with FPIES as sometimes the two conditions co-exist or one form transforms into the another. International consensus guidelines own been developed for FPIES.(18)
Food protein-induced allergic proctocolitis (FPIAP)
FPIAP is a benign transient condition, typically starting in the first few months of life with bloody stools in well-appearing infants.
About 60% of cases happen in breast-fed babies, the remainder in infants fed cow's milk or soy protein-based formulas.
Rarely, dietary protein proctitis shows mild hypoalbuminaemia and peripheral eosinophilia. Bowel lesions are generally confined to distal large bowel; endoscopy reveals linear erosions and mucosal oedema with infiltration of eosinophils in the epithelium and lamina propria.
Food-induced pulmonary haemosiderosis (Heiner's Syndrome)
This extremely rare syndrome, affecting infants and young children, is characterized by recurrent episodes of pneumonia associated with pulmonary infiltrates, haemosiderosis, gastrointestinal blood loss, iron deficiency, anaemia, failure to thrive.
It is due to cow's milk(19); the immunologic mechanism is still unknown.
Mixed IgE and non-IgE reactions
Although it is not, strictly speaking, an allergic disease, at least one-third of infants and young children with atopic eczema own IgE-mediated food allergy. Egg allergy is the most common food hypersensitivity in children with eczema. Appropriate diagnosis of food allergy and elimination of the offending allergen leads to significant clearing or improvement of eczematous lesions in numerous young children with eczema and food allergy.
Food allergens may be triggers for some acute exacerbations (20).
Allergic eosinophilic oesophagitis (EoE).
This condition may present in children with a variety of nonspecific symptoms, e.g., feeding difficulty, nausea, vomiting, heartburn, and failure to thrive. Teenagers and adults are more likely to present with dysphagia and episodes of food impaction.
Eighty percent of patients with eosinophilic esophagitis own symptoms similar to gastroesophageal reflux, which are refractory to anti-reflux therapy. In the case of infants, the vomitus often contains stringy mucus (similar to egg albumin). Patients may also present with food refusal, dysphagia, food impaction or abdominal pain.
Food induced IgE-mediated allergy has been implicated in the pathogenesis in some patients. In eosinophilic esophagitis there may be years of unrecognized childhood subclinical disease or “silent” chronic inflammation before the diagnosis is made.(21)
Allergic eosinophilic gastritis or gastroenteritis
The exact cause of these disorders remains unknown although both IgE-mediated and T-cell-mediated reactions own been implicated. These conditions are characterized by infiltration of eosinophils in the mucosal, muscular and/or serosal layers of the stomach or little intestines.
Patients present with postprandial nausea and vomiting, abdominal pain, diarrhea (occasionally steatorrhea) and weight loss in adults and failure to thrive in young infants.
Diagnosis of Food Allergy
The results of skin prick tests (SPT), IgE entire and specific antibodies, and patient histories are not predictive of true food allergy, as they are not capable to establish the causal and temporal relationship between the intake of the suspect food and the hypersensitivity reaction. The negative predictive accuracy of a skin prick test weal of < 3mm greater than the negative control is high, generally > 95%, and is strong evidence that the food may be consumed without severe, immediate food-allergic reactions.
A positive SPT, even a weal of 3 mm or more, may be clinically irrelevant, as the patient may tolerate the ingested food. SPTs may also remain positive after the development of tolerance to the specific food.
Specific IgE levels display a variable diagnostic accuracy according to the nature of the allergen, the studied population, the specific brand of the test. Using the most favorite diagnostic systems, in is conventionally accepted that kU/l is the cut-off level for a positive in-vitro test of specific IgE.
Higher levels of specific IgE for food allergens may better correlate with clinical reactivity as evidenced by challenge testing. For this reason, decision points own been proposed. While valid in the studied populations, the worth of such decision points cannot be universal (see table below).
A double blind, placebo-controlled food challenge (DBPCFC) is the preferred test to diagnose food allergy3,19. DBPCFC should be performed in specialist centers with shut supervision. Resuscitation facilities and overnight admission can be necessary in severe cases. DBPCFC is hard to organize in numerous clinical situations, and can be replaced by open challenges in numerous situations (when there is a minimal risk of untrue interpretations due to subjective factors).
When a psychological reaction is strongly suspected, a single-blinded test may also be used (22, 23).
The in vitro diagnostics can assist to identify cross-reactive allergens between pollen and foods, or foods and latex. Cross-reactive allergens include common lipid transfer proteins (LTPs), PR molecules, and profilin. Skin prick/puncture tests using commercial extracts to the implicated fruit are often negative, but a positive test may be obtained using a drop of unused juice from the incriminated fruit.
The atopy patch test (APT) is an epicutaneous skin test in which allergens commonly associated with IgE reactions can be used, although patch testing is more commonly performed for metals such as nickel, which causes a positive patch test in nickel sensitive subjects.
Although the pathogenic mechanisms of the APT own not been fully elucidated, a positive APT can predict a tardy phase reaction following oral food challenge. A positive APT may detect clinically relevant tardy phase eczematous or GI reactions in infants and children (24). This test is not useful for IgE-mediated food allergy. It is considered experimental in most parts of the world (25).
Prevention of food allergy
According to every the current guidelines, an baby with at least one first-degree relative (parent or sibling) with a history of allergic disease’ (26, 27) in specific allergic rhinitis, asthma, eczema, or food allergy (28, 29) is at greater risk for developing food allergy.
The first proposed recommendation for a large-scale prevention of food allergy has been the use of hypoallergenic (HA) formulae in case of breastfeeding failure.
This approach has reached the level of evidence to be included in the NIAID recommendations on food allergy prevention (30), but it has subsequently been questioned. (31) Earlier guidelines on allergy prevention recommended delayed exposure to solid foods, avoidance of allergenic foods, and did not include interventions aimed at promoting the infants’ immune tolerance (32). Emerging evidence, however, has led to a paradigm shift, supporting nutritional approaches such as appropriate timing of food exposure, and use of prebiotics and probiotics for allergy prevention.
The Learning Early about Peanut (LEAP) study showed that early introduction of peanuts significantly decreased the frequency of peanut allergy among children at high risk, and modulated immune responses to peanuts (33). Hence, based on these findings, the National Institutes of Health (NIH) Guidelines for the Management and Prevention of Food Allergy subsequently recommended the introduction of peanut-containing foods to “high-risk” infants early in life ( months) (34).
The World Allergy Organization (WAO)/McMaster Working Group Guidelines for Allergic Disease Prevention (GLAD-P) has also published GRADE recommendations on the use of probiotics and prebiotics for allergy prevention based on current available evidence.
The guideline panel suggested using probiotics in pregnant and breastfeeding women whose children and infants are at high risk for developing allergy29. Probiotics own been shown by numerous studies to be effective in allergy prevention, particularly in reducing allergic eczema at a rate of 9 fewer cases per pregnant women (risk ratio [RR] ), 16 fewer cases per breastfeeding women (RR ), and 5 fewer cases per infants (RR ). Ultimately, the use of probiotics should be individualized and further studies are needed to assess their effect in preventing other types of allergy and the differences among the strains of the same species of probiotic bacteria.
Concerning prebiotics, GLAD-P conditionally recommends prebiotic supplementation in non-exclusively breastfed infants, both at high and at low risk for developing allergy, but not in exclusively breastfed infants (35). These recommendations were largely based on a meta-analysis of available evidence showing that prebiotic supplementation reduces the risk of developing asthma or recurrent wheezing (RR: , 95 % CI: to ) and the risk of developing food allergy (RR: , 95 % CI: to ) (36). It has been proposed that these effects result from interactions between the gut microbiota and the gut mucosal immune system.
GLAD-P provides no recommendation at this time on prebiotic use in pregnant and breastfeeding women, owing to the lack of evidence from experimental and observational studies.
In the future, the GLAD-P guidelines may be expanded as more data from rigorously designed, adequately powered and well-executed trials become available.
Recommendations on other interventional measures, such as vitamin D supplementation, in allergy prevention are negative (37).
Food Allergen Avoidance
The foods to which an individual is allergic should be avoided, as therapeutic intervention (tertiary prevention) in patients with food allergy. It must strike a precautionary equilibrium between the demands of prohibitive measures against allergy care and quality of life. Such a dynamic endpoint is hard to assess for efficacy and safety. Avoidance measures need to be tailored to the individual’s life and disease requirements must take account o the needs of growth, the prevention of anaphylaxis and, of the benefits expected of allergen avoidance itself.
From the patient’s perspective, avoidance means meeting obstacles unshared by their non-allergic peers, thereby curtailing their quality of life.
From the physician’s outlook, education, ensuring compliance and receptiveness of both patient and caregiver are major concerns. The role of the allergist is to review in a dialectical assessment these competing factors in concert with every parties concerned. Where avoidance of the implicated food may result in nutritional deficiency, dietary supplementation is necessary3.
Processed foods may contain hidden proteins, e.g., milk, egg and soy proteins may be added to increase the protein content or enhance flavor.
Peanuts and nut products are added to thicken and flavor sauces. Patients can be taught to identify hidden food components in processed foods. Commonly used ‘hidden' proteins are casein and lactose, derived from milk, and albumin from egg. To reveal hidden food allergens, food labelling is an issue of relevance to food allergic consumers of processed or pre-packaged foods. In the European Union, 12 food items are required by law to appear on the label: cereals containing gluten, crustaceans, egg, fish, peanut, soy, milk (including lactose), tree nuts, mustard, sesame seeds, celery, and sulfites >10 mg/kg (38).
Similar legislation is in effect in the US, where the Food Allergen Labeling and Consumer Protection Act provides that every food products require an ingredient statement. In these countries, the legislation has altered industry practices in some significant aspects for milk, egg, peanut, tree nuts, shellfish, fish, soy and wheat. In other countries, hidden allergens can be exempt from specific labeling, and thus be inadvertently consumed by food allergic individuals. On both the sides of Atlantic, the regulatory problem is now the opposite concern, that is, whether too numerous foods containing trace amounts of these allergenic foods are being "overlabeled" and whether this would then potentially restrict potentially safe food choices for allergic consumers.
In fact, the labeling regulations do not prescribe the indication of potential contaminants, but numerous manufacturers are now indicating, “may contain” as a warning of potential contaminations during food preparation (39).
Hypersensitivity reactions are often treated with medications. . Epinephrine is the only medication that is effective for the treatment of anaphylaxis. Additional medicatioons include H1 and H2 antihistamines, corticosteroids, and prostaglandin synthetase inhibitors These drugs are only symptomatic, do not modify the natural course of the disease, and sometimes own unacceptable side effects.
Anti-IgE monoclonal antibodies therapy is licensed for use in asthma and for chronic urticaria in numerous countries, and studies are under way to determine if it has a role in the management of serious food allergies.
Any desensitisation protocol to both reduce the risk of major reactions and avoid nutritional restrictions in children suffering from food allergy would be highly beneficial. The subcutaneous istration of native (40) or modified (41) peanut extracts was attempted in the past, but the shots induced systemic reactions or serious adverse effects.
In the final years, the experience with oral immunotherapy has made this a common, accepted treatment in some countries. A recent systematic review concluded that oral immunotherapy is no longer experimental, but is ready for practical application (42). It should be applied to reduce the risk of inadvertent reactions, and not to modify the natural course of the disease (43).
“Tolerance” in “desensitized” children disappears if the allergen is not ingested every day in therapeutic doses. However, research is ongoing and the future use of recombinant allergens (44), synthetic peptides (45),and epicutaneous therapy for desensitization in humans looks more promising (46).
One of the most often asked parents’ questions is “How endless will my child’s food allergy last?” Given the present impossibility to modify the natural history of food allergy, the answer must take into account a series of factors.
There is a relationship between symptom severity after ingestion and the likelihood of outgrowing the problem; the more severe the reaction, the less likely that the food allergy will be outgrown. Other factors, such as sIgE antibody level and age at diagnosis, own also been associated with prognosis of food allergy, although these associations are not invariably consistent across studies (47, 48, 49). Milk allergy’s half-life is approximately two years while egg allergy’s half-life is approximately four years. Peanut allergy, once considered to be a life-long condition, can resolve in up to 30% of cases (50).
However, it is not possible to establish a half-life for a diagnosis of peanut allergy and tree nuts should still be considered as lifelong allergies.
Similarly, fish allergy is considered a long-lasting condition and reports of recovery are rare (51). However, no study has evaluated the natural history of fish allergy in infants and fish should also be regarded as causing persistent allergies.
While peanut, tree nut, fish and seafood allergy are mostly persistent conditions, little is known about the natural history of allergy to such staples as fruits, vegetables, cereals and meat.
In food allergic children, tolerance must be tested by oral challenge at regular intervals.
Often tolerance is not acquired suddenly, but there is a gradual increase of the doses tolerated at challenge. Even after years of apparent clinical tolerance, gastrointestinal symptoms of food allergy and reduced growth, . Epinephrine is the only medication that is effective for the treatment of anaphylaxis. own been reported (52).
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ANAPHYLAXIS: A Severe Allergic Reaction
Types of food allergies
Food allergies are divided into 3 types, depending on symptoms and when they occur.
- non-IgE-mediated food allergy – these allergic reactions aren’t caused by immunoglobulin E, but by other cells in the immune system.
This type of allergy is often hard to diagnose as symptoms take much longer to develop (up to several hours).
- IgE-mediated food allergy – the most common type, triggered by the immune system producing an antibody called immunoglobulin E (IgE). Symptoms occur a few seconds or minutes after eating. There’s a greater risk of anaphylaxis with this type of allergy.
- mixed IgE and non-IgE-mediated food allergies – some people may experience symptoms from both types.
Read more information about the symptoms of a food allergy.
Oral allergy syndrome (pollen-food syndrome)
Some people experience itchiness in their mouth and throat, sometimes with mild swelling, immediately after eating unused fruit or vegetables.
This is known as oral allergy syndrome.
Oral allergy syndrome is caused by allergy antibodies mistaking certain proteins in unused fruits, nuts or vegetables for pollen.
Oral allergy syndrome generally doesn’t cause severe symptoms, and it’s possible to deactivate the allergens by thoroughly cooking any fruit and vegetables.
The Allergy UK website has more information.
The best way to prevent an allergic reaction is to identify the food that causes the allergy and avoid it.
Research is currently looking at ways to desensitise some food allergens, such as peanuts and milk, but this is not an established treatment in the NHS.
Read more about identifying foods that cause allergies (allergens).
Avoid making any radical changes, such as cutting out dairy products, to your or your child’s diet without first talking to your GP. For some foods, such as milk, you may need to speak to a dietitian before making any changes.
Antihistamines can assist relieve the symptoms of a mild or moderate allergic reaction. A higher dose of antihistamine is often needed to control acute allergic symptoms.
Adrenaline is an effective treatment for more severe allergic symptoms, such as anaphylaxis.
People with a food allergy are often given a device known as an auto-injector pen, which contains doses of adrenaline that can be used in emergencies.
Read more about the treatment of food allergies.
Most food allergies affect younger children under the age of 3.
Most children who own food allergies to milk, eggs, soya and wheat in early life will grow out of it by the time they start school.
Peanut and tree nut allergies are generally more endless lasting.
Food allergies that develop during adulthood, or persist into adulthood, are likely to be lifelong allergies.
For reasons that are unclear, rates of food allergies own risen sharply in the final 20 years.
However, deaths from anaphylaxis-related food reactions are now rare.
What causes food allergies?
Food allergies happen when the immune system – the body’s defence against infection – mistakenly treats proteins found in food as a threat.
As a result, a number of chemicals are released.
It’s these chemicals that cause the symptoms of an allergic reaction.
Almost any food can cause an allergic reaction, but there are certain foods that are responsible for most food allergies.
Foods that most commonly cause an allergic reaction are:
- tree nuts
- some fruit and vegetables
Most children that own a food allergy will own experienced eczema during infancy.
The worse the child’s eczema and the earlier it started, the more likely they are to own a food allergy.
It’s still unknown why people develop allergies to food, although they often own other allergic conditions, such as asthma, hay fever and eczema.
Read more information about the causes and risk factors for food allergies.
In the most serious cases, a person has a severe allergic reaction (anaphylaxis), which can be life threatening.
Call if you ponder someone has the symptoms of anaphylaxis, such as:
- trouble swallowing or speaking
- breathing difficulties
- feeling dizzy or faint
Ask for an ambulance and tell the operator you ponder the person is having a severe allergic reaction.