Food Allergy vs. Food Intolerance – Part 1: Allergies

It’s very common (dare I say, trendy) these days to pronounce an aversion to a certain food or food group based on a food allergy or intolerance. Last month on the blog we talked about why going gluten-free doesn’t necessarily make you healthy. To give you a little more background, and to help you make an informed decision about what you decide you can or cannot eat…let’s take a look at allergies and intolerances.

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To discuss food allergy and food intolerance in one blog post is super ambitious, so I am breaking it up into two. For Part 1, let’s look at allergies and coeliac disease, which are two categories of the most severe reactions you can have to a food or ingredient. In Part 2 we will cover food intolerance and some general guidance about whether you really need to avoid certain foods.

Food Allergy

An allergic reaction is an immune system-moderated reaction to what is otherwise a harmless exogenous (i.e. not part of you) substance. Part of your body’s specific immune system are little proteins called immunoglobulins a.k.a. antibodies. You have five types (yes like the Power Rangers, if you remember them), referred to as IgA, IgD, IgE, IgG and IgM. They each have a different role to play in responding to substances that your body recognises as harmful.

The IgE immunoglobulin is the antibody that is activated in a true “allergic” reaction. Basically, what happens is that your body recognises a substance as bad and manufactures some IgE antibodies that are specifically targeted to attack that substance to protect you. That’s the thing about antibodies; there is not just one general “IgE” floating around in all of us; your body makes up specific IgEs that only have eyes for one thing. So, a specific IgE gets produced and in the course of attacking the substance you develop symptoms of an allergic reaction, which, in the case of an allergy to food, can include:

• itching, tingling, redness and swelling of the mouth/face;
• a skin rash;
• wheezing, difficulty breathing and/or swallowing;
• nausea, vomiting, tummy pain, upset stomach;
• light-headedness;
• feeling like you have hay fever e.g. sneezing, itching eyes.

The most serious IgE allergic reaction, anaphylaxis, is when you experience the redness, swelling, wheezing etc. symptoms described above but very intensely, coupled with a rapid heartbeat, a drop in blood pressure and difficulty breathing. This can lead to unconsciousness and even death.

Allergic reactions to food have an immediate onset*, and as you can appreciate from the above, feel terrible. The most common food allergens causing an IgE reaction are peanuts, milk, eggs, soy and shellfish. If you have a significant allergy to a certain food or ingredient in food chances are you don’t need to read this article to get a better understanding of your condition. Man, you know about it. You absolutely cannot eat that food, without becoming unbelievably ill, even being unable to breathe. It is the most severe type of reaction you can have to a food/ingredient. Some people may experience a milder allergic reaction to food but one that is nevertheless pretty darn uncomfortable.

Allergies can be identified by skin prick or blood testing; some hospitals have specialised allergy units that undertake rigorous testing on individuals to pinpoint multiple food allergies.

A special case: Coeliac (celiac) disease

Coeliac disease, also sometimes referred to as a gluten allergy, is an autoimmune disease. This is kind of like an allergic reaction, except that instead of attacking a foreign substance, your body starts attacking itself. This happens because your body gets confused and manufactures antibodies that target you, instead of something external to you. In coeliac disease, this antibody production is triggered by the consumption of gluten.

When a coeliac consumes gluten, it stimulates the production of IgA and IgG antibodies that turn around and start attacking the lining of the small intestine. Picture the inside of your intestine like the frilly seaweed ocean floor, like you saw in The Little Mermaid (don’t you love my childhood references in this piece?). Your antibodies destroy the frilly projections (actually called villi), whose purpose is to help you absorb nutrients from food; the villi act like little fingers and catch things. With the villi damaged your gut lining is less effective, causing malabsorption, indigestion and discomfort… and leading to feeling generally weak and unwell because you aren’t getting much from your food.

Symptoms of coeliac disease are quite broad and many are nonspecific. Coeliac UK give the following list:

• severe or occasional diarrhoea, excessive wind and/or constipation;
• persistent or unexplained gastrointestinal symptoms, such as nausea and vomiting;
• recurrent stomach pain, cramping or bloating;
• any combination of iron, vitamin B12 or folic acid deficiency;
• anaemia;
• tiredness;
• sudden or unexpected weight loss (but not in all cases);
• mouth ulcers;
• hair loss (alopecia);
• skin rash (dermatitis herpetiformis);
• tooth enamel problems;
• depression;
• liver abnormalities;
• repeated miscarriages;
• neurological (nerve) problems such as ataxia (poor muscle coordination) and neuropathy (numbness and tingling in the hands and feet).

Coeliac disease can make people feel extremely unwell, and because of the damage the antibodies can do to the intestinal lining, it is essential that affected individuals avoid consuming products containing gluten. In addition to avoiding products that are obviously based on the gluten-containing grains like wheat, rye, barley and spelt, coeliacs must be vigilant about commercially made condiments, sauces, dips and seasonings which are often derived from such grains e.g. soy sauce, gravy, seasoned snack foods like potato chips…the list is enormous.

Coeliac disease can be identified by a blood test; the test looks for certain antibodies in your bloodstream. IgA Anti-tissue Transglutaminase Antibody (TTG) is the primary antibody that will be looked for but there are others (you can read more on this lab tests website).

Tested positive for a food allergy or coeliac disease?

If you have a diagnosed food allergy** or coeliac disease, then, generally speaking, you need to be careful about what you eat and you really must not eat any food products containing/prepared next to/otherwise contaminated with the offending substance. When you’re buying pre-made food or eating out, it is sensible and reasonable for you to question the menu and request a free-from option if not obviously available, because you can become so ill. Restaurants and caterers must (well, technically they must, I can’t guarantee it) specially prepare your food if you notify them.

When it’s not a food allergy or coeliac disease?

Come back for Part 2 when I talk about food intolerance!

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*There is another type of allergic reaction to food (technically speaking, a Type IV hypersensitivity reaction) which is a little less common, and has a delayed onset, typically between 8-72 hours. This is not an IgE reaction and is more difficult to detect; the orthodox way of investigating this is an elimination diet. It can still cause quite severe and uncomfortable symptoms like a rash/eczema type skin reaction, bloody or mucous-containing stools and significant digestive discomfort.

**Note that some allergies diagnosed in childhood will not remain for life; you can outgrow them so if you’re not reacting anymore – it’s not too good to be true!