Food Intolerances and Allergies

See also: Stress, Nutrition and Diet

Food intolerances and allergies seem to be increasing. But is that really the case, or are we just more aware of problems now?

Are food intolerances just a fashionable way to draw attention to ourselves, and make life more difficult for others?

And what exactly is the distinction between an intolerance and an allergy?

This page explores and answers these questions and others, to help you navigate your way through what sometimes feels like a very modern problem.


Defining Allergies and Intolerances

Although the terms are sometimes used interchangeably, allergies and intolerances are not the same.

A food allergy is a reaction from your immune system that occurs soon after you have eaten or come into contact with certain foods.

It can happen immediately or after a short time, but is generally not long delayed. The reaction can also be triggered by very small amounts of food; in some cases, simply breathing in dust from the allergen can cause a reaction. Symptoms can include a skin rash, swelling, including in the mouth and throat (which can block the airway) and nausea. An extreme allergic reaction, known as anaphylactic shock, can occur in some sufferers of food allergies. It affects all body systems, and can be life-threatening.


A food intolerance is a more delayed reaction to a food or substance found in a food.

It is generally much less severe and immediate than a food allergy. Symptoms are often limited to digestive issues, although they can also include skin problems and headaches.

In other words, allergies are reactions linked to your immune system. Like the reaction that you get when you are stung by a bee or wasp, or touch a nettle, they are rapid. They often result in swelling which can, if in the mouth or throat, potentially be fatal.

Allergies can usually be treated with anti-histamines taken orally. This includes for vomiting and skin conditions.

Serious allergic reactions (including anaphylaxis), however, require rapid treatment with adrenaline to prevent potentially fatal consequences.

Most people who are severely allergic to something, including a food, are aware of their allergy and carry an adrenaline pen (sometimes called an ‘EpiPen’). Even after treatment, they should still seek medical advice as soon as possible after having an allergic reaction.

Food intolerances, on the other hand, are not potentially fatal, and people with intolerances can sometimes be unaffected by consuming a small amount of the problem food. Intolerances can, however, be extremely uncomfortable, and can make people feel quite unwell, often over a long period of time, if undiagnosed.


Causes and triggers of allergies and intolerances

The precise cause of an allergy is often unclear.

Some studies have suggested that the problem is under-exposure: that people are more likely to be allergic to things that are new to their immune system. Allergies can also, however, be triggered by rapid over-exposure to the allergen in a sensitive part of the body (for example, if you are stung on the face or head by a wasp, you may become very allergic to wasp stings).

However, there is often no obvious trigger point, and people only become aware that they are severely allergic when they first react.

Perhaps the best-known food allergy is to peanuts.

This is, anecdotally at least, on the increase. It is, however, more likely that peanuts and other nuts are simply becoming more common, because they are included in a wide range of processed foods. People are therefore more likely to be exposed to them than in the past, and become aware that they are allergic.

There are several clear potential causes of food intolerances:

  • Sufferers may lack the enzyme needed to digest the food. For example, lactose intolerance is often caused by not having a gene for the enzyme that digests it.
  • Sensitivity to food additives. Some people are more sensitive to certain chemicals than others, and this can cause problems when they are added to food. Examples include food colouring and sulphites, which are used in drying fruit.
  • People with coeliac disease are unable to digest gluten properly, and are therefore intolerant of it.
  • There may also be psychological factors involved in food intolerances. For example, some people are simply unable to swallow certain foods, without any obvious physical cause.

Identifying and Managing Food Allergies

Food allergies are severe enough that identifying their existence is often not hard. However, identifying the trigger can be more difficult, not least because you cannot risk anaphylactic shock to do so.

The key to treating allergies is often avoidance, so it is important to identify the allergen as early as possible.

Identifying allergens

There are two main tests for allergens:

  1. A ‘scratch test’, where the skin is exposed to a small amount of potential allergens to test for a reaction; and
  2. A blood test, which can be used if a skin test is not appropriate.

Those who have experienced a severe allergic reaction should therefore discuss this with a doctor, to have a test for potential allergens as soon as possible.

These tests not only identify the allergen, but also give an idea of the intensity of the reaction. When the reaction is very severe, you may need to do more than simply avoid eating that particular food. For example, it may be necessary to ask schools or workplaces to ensure that they are ‘nut-free’ for the safety of a particular individual, and you may also need to inform airlines when flying.

Identifying and Managing Food Intolerances

Identifying food intolerances may be less critical than allergies, but it is also harder. There is unlikely to be an immune reaction involved, and therefore there are few, if any, definitive tests.

There are two main ways to identify triggers: using a food diary, and removing and replacing certain foods. The most usual approach is likely to involve both.

Using a food diary to identify potential triggers


WARNING! This is best done under the supervision of a trained dietician or nutritionist, who is more likely to be able to identify likely triggers. However, as a first step, you can do this yourself.

  1. Over a period of several weeks or a month, keep a diary that sets out everything you eat, right down to a biscuit and a cup of tea or coffee, and the precise time.
  2. Also keep a note of any symptoms that you have, including minor ones, and the time at which they occurred.
  3. Try to spot any patterns that are emerging. Are there certain foods, combinations of foods, or even ingredients that seem to cause you particular problems?

WARNING! Triggers are not always obvious, and it helps to be aware of the ingredients of what you eat. It is easier to do this when you cook your own food, rather than eating ready meals or eating out.

  1. If you spot a potential trigger, try cutting it out of your diet for a few days and see what happens.
  2. You may find that you have more than one trigger. For example, some people are both lactose- and gluten-intolerant.

When a food intolerance is very severe, nutritionists sometimes advise cutting a wide range of potential triggers out of your diet all at once. This is designed to allow the symptoms time to settle, before you add back in potential triggers one at a time, to see which ones have an effect.

WARNING! This is not something to try at home without the supervision of a qualified healthcare professional.

It can lead to problems such as becoming malnourished if you do it for too long. It can also mean that underlying conditions are not diagnosed.


The bottom line

The best advice if you think you may be suffering from a food intolerance or allergy is to talk to your doctor, and ask for a referral to a specialist clinic.

They are best-placed to help you identify the trigger, or any underlying condition, safely.

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