What is the key difference between food allergy and food intolerance

What is the key difference between food allergy and food intolerance

An allergy is a response by the body’s immune system to something (called an allergen) that is not necessarily harmful in itself. Certain people are sensitive to this allergen and own a reaction when exposed to it.

What is the key difference between food allergy and food intolerance

Some allergic reactions are mild and harmless, but others are severe and potentially life-threatening (anaphylaxis). (See the separate leaflets called Allergies and Anaphylaxis for more information.)

What is a food allergy?

A food allergy is an abnormal reaction of the body’s immune system to a specific food. This tends to cause unpleasant and unwanted effects (symptoms).

There are diverse types of food allergy, depending on which part of the immune system responds.

What is the key difference between food allergy and food intolerance

The acute, sudden-onset reactions tend to be caused by antibodies called immunoglobulin E (IgE). These are called IgE-mediated reactions. As a result of these reactions, various chemicals are made, including histamine. Histamine causes numerous of the allergy symptoms and this is why antihistamines can be used to treat some allergic reactions.

There are also non-IgE-mediated reactions which tend to be more delayed and less severe. In these reactions the symptoms are not caused by IgE. Instead other parts of the immune system, such as a type of white blood cell, called a T cell, cause the problem.

Common reactions include skin problems such as rashes and eczema, and tummy (abdominal) symptoms and bowel disturbance.

It is also possible to own mixed reactions.

What is a food intolerance?

A food intolerance is not the same as a food allergy. Numerous people incorrectly use the words interchangeably.

What is the key difference between food allergy and food intolerance

A food allergy is the body’s immune system reacting abnormally to specific foods. No allergic reaction takes put with a food intolerance.

People with a food intolerance may own digestive symptoms such as diarrhoea, bloating and stomach cramps. These are fairly common symptoms anyway. For example, other conditions, such as irritable bowel syndrome (IBS), can also cause these symptoms.

In food intolerance, the symptoms can be caused by various problems. Although the immune system is not involved, it does not mean that symptoms of food intolerance are unimportant or mild in nature. Food intolerance can cause considerable problems and significant symptoms.

Some examples are:

  1. Direct effects of foods and additives.

    Certain foods and chemicals in foods may directly affect the body and cause symptoms. For example, some people discover that the food additive monosodium glutamate (MSG) causes flushing, headache, abdominal pains and bloating. However, the exact way in which foods and additives may cause symptoms is often not clear.

    There is controversy about whether certain additives (E numbers) are responsible for various symptoms, especially in children. Also, there is uncertainty as to whether certain foods can make symptoms worse in some people who own conditions such as IBS, migraine and eczema.

  2. Lactose intolerance. This causes diarrhoea and tummy (abdominal) symptoms (bloating and pain) after milk is drunk or dairy products are eaten.

    It happens because of a deficiency of lactase, an enzyme in the body that digests the sugar in milk (lactose). Unless lactose is broken below, the body cannot absorb it. You can be born without any lactase, or only a low level, or you can develop lactase deficiency — often after an episode of infection of the gut (gastroenteritis). See the separate leaflet called Lactose Intolerance for more details.

  3. Food avoidance. Some people, especially children, may develop physical symptoms such as feeling ill and diarrhoea if they eat, or are offered, foods they own come to dislike.

    Strictly speaking this is not a true food intolerance. It may, however, be hard to distinguish between avoidance and intolerance in children.

Also, numerous people incorrectly assume symptoms they own are due to food intolerances when in fact their symptoms are not due to food. Consequently, people commonly cut things out of their diet that they believe to be the cause of their problems. In itself this can lead to further problems.

In summary, food intolerance often ends up being a rather vague term which is sometimes hard to clarify.


Food allergy

Symptoms of food allergy due to an IgE allergic reaction include:

  1. Sneezing or a runny nose.
  2. Tingling in the mouth.
  3. A rash and/or itching of the skin — the rash may be raised, blotchy and red or the skin may be flushed.
  4. Feeling ill or being ill (vomiting).
  5. Itchy, reddened, watery eyes.
  6. Diarrhoea.
  7. Wheezing or feeling breathless.
  8. Swelling of the lips, tongue or throat, which in severe cases can make it hard to swallow or breathe.
  9. Swelling of the face around the eyes.
  10. Tummy pain.
  11. Feeling light-headed.

These symptoms tend to happen immediately, or shortly after, eating the trigger food.

Symptoms of food allergy due to a non-IgE allergic reaction include:

  1. Redness around the back passage (anus).
  2. Atopic eczema (classical eczema) that is seen in allergy-prone (atopic) families — often those with hay fever and asthma too.
  3. Vomiting that is generally effortless (gastro-oesophageal reflux).
  4. Blood or mucus in the stools.
  5. Tiredness.
  6. Constipation.
  7. Loose and/or frequent stools (faeces).
  8. Being pale (pallor).
  9. Poor growth.

    This is often seen in children with a non-IgE food allergy. Young children, particularly those with digestive symptoms, should be regularly weighed. Weight should be plotted on a growth chart. This allows medical professionals such as GPs and health visitors to see if growth is slow.

These are every possible symptoms of a food allergy. They range from the mild reactions and chronic symptoms to the most severe and life-threatening ones.

Food intolerance

Symptoms of a food intolerance vary widely and can include:

  1. A runny nose.
  2. Bloating and tummy (abdominal) pain.
  3. Diarrhoea or loose stools.
  4. Skin rashes and itching.
  5. Feeling tired.
  6. Headaches.

Some of these symptoms are the same as those which can be caused by a non-IgE food allergy.

So this shows how complicated it can be to determine whether you own an allergy or an intolerance.

How common are reactions to food?

It is extremely hard to know how common true food allergy really is. Studies tend to come up with extremely diverse figures.

What is the key difference between food allergy and food intolerance

depending on how they are set up. They propose that in the developed world anywhere between 1 and 17 people out of own a food allergy. People tend to report food allergy more often than it is confirmed by formal testing. Numerous people mistakenly believe they own food allergies. Also, children can ‘grow out’ of allergies — for example, to cow’s milk. The number of people with food allergies seems to be rising. However, the severity of these allergies varies.

What is the difference between food allergy and food intolerance?

With a food allergy, there is an abnormal reaction of the body’s immune system to a specific food.

This can range from a mild reaction to one that is severe and life-threatening (anaphylaxis). Food intolerance happens because the body has difficulty digesting certain substances in food, or because certain substances own a direct effect on the body in some way. Food intolerance can cause symptoms such as diarrhoea, bloating and stomach cramps. However, with food intolerance there is no allergic reaction and the immune system is generally not involved.

The symptoms of food intolerance happen generally a few hours after eating the food.

Allergic reactions generally happen much more quickly.

With an allergy, even a tiny quantity of the food can cause an allergic reaction to take put. Some people with a severe allergy to nuts might experience an extreme form of allergic reaction (anaphylaxis):

  1. After eating something made in a factory that also handles nuts; or
  2. After kissing someone who has recently eaten nuts.

With food intolerances you need a lot more of the food to cause the symptoms.

Food intolerances are never life-threatening.

Some allergies are, as they can cause anaphylaxis.

Mouth and throat (oral) allergy syndrome

Some people get a type of allergic reaction to certain foods that only causes symptoms in the mouth and throat. It tends to cause itching, tingling, and swelling of the mouth, lips and throat. Unused fruit, vegetables and nuts commonly cause this. It can be confused with an extreme form of allergic reaction (anaphylaxis).

It has the potential to be serious, as swelling in the mouth and throat can affect the ability to breathe; however, this is rare. The symptoms start within minutes of eating and tend to settle completely within an hour. Often if you own this condition, you can eat cooked versions of these foods with no problem, but the raw food gives you symptoms.

What is the key difference between food allergy and food intolerance

This is because the proteins causing the allergic reaction are destroyed by the cooking process. Oral allergy syndrome generally affects people who get hay fever, and may also be called pollen food syndrome.

Note: an ambulance should be called immediately if you feel faint, own difficulty breathing or feel love your throat is closing up.