Allergy Definitions

Allergy and Intolerance Definitions: As Clear As Mud!

Just what is an allergy or an intolerance? What’s the difference between them? How is lactose intolerance different to dairy intolerance? Is gluten intolerance the same as coeliac disease? 

This area of medicine is a minefield, with confusion in all sectors. The problem comes because health professionals and lay people use the various definitions and terms interchangeably, and what the doctor may understand by a term may not match what Joe Public thinks it means.

I thought it might be an idea to start with some definitions for you so here is some info largely based on a blog post from Michelle at which should help.



The medical definition of food allergy is an immediate immune system reaction sparked by the binding of an IgE antibody to a mast cell thereby causing a release of histamine. It is this type that confers a risk ofanaphylaxis.

The medical definition of  food intolerance is a delayed reaction to a food which does not involve the immune system, the symptoms of which are extremely varied and can be behavioural/psychological as well as physical. It is worth noting that a reaction may only be ‘delayed’ by a matter of minutes, but is usually from 2-4 hours later and can last several days.

These definitions tend only to be understood by the medical profession – and not by all of them!!

The average food intolerance sufferer thinks of him/herself as a food allergy sufferer which explains the huge divergence between the ‘official figures’ for food allergy (1-2% of the population) and the popular perception (30-40% of the population). Dietitians, in particular, get very exercised about this…..

In fact, there is a sense that allergy is worse to have than food intolerance and that is understandable because of the risk of anaphylaxis. However, food intolerance sufferers are often sensitive to more foods and have more frequent reactions affecting more body systems so it can be awful to live with in a different way.

Even though the accepted medical definition of a food intolerance is non-immune, some types of reaction, but not all, do involve antibodies such as IgG, IgA and IgM.


Cow’s milk allergy and lactose intolerance

Cow’s milk allergy is an immune response (see allergy above) to one or more proteins in cow’s milk – can be anaphylactic.

Cow’s milk intolerance is a food intolerance (see intolerance above) to some or all the constituents (not necessarily proteins) in cow’s milk so is more likley a delayed reaction.

Lactose intolerance is not, strictly speaking, an intolerance at all but a deficiency of the enzyme lactase which digests the lactose sugar in milk. In lactose intolerance the undigested lactose sugar ferments in the gut giving the typical digestive symptoms of lactose intolerance.

Lactose intolerance has nothing to do with cow’s milk allergy and although it is possible to suffer from both, they are totally separate conditions. Very few outside the medical profession understand the differences so the three terms are used indiscriminately.


Coeliac disease, gluten sensitivity/intolerance, gluten-related disorders, wheat allergy, wheat intolerance and maldigestion

Gluten-related disorders (GRDs). This is a new definition coined in recognition of the fact that there is now thought to be a ‘syndrome’ or ‘spectrum’ of gluten illnesses. GRDs can go all the way from coeliac disease to gluten intolerance. For more on this, see here.

Coeliac disease is an autoimmune condition in which the protein fraction, gliadin, found in wheat, barley and rye, causes the villi or fronds which line the small intestine to atrophy, thereby preventing the sufferer absorbing nutrition from what they eat and preventing its proper digestion. It can have wide ranging symptoms many of which may be digestive, but need not be. It is thought to affect around  1 in 70 of the population although it is also thought to be heavily under-diagnosed.

Non-coeliac gluten sensitivity (NCGS). NCGS is now thought to be quite common and far more so than coeliac disease. This goes some way to explaining why so many people feel better on a gluten free diet but who do not fit the coeliac diagnostic pattern.

Research is still continuing but essentially where coeliac disease is an autoimmune disease with gluten sparking an attack on the villi, NCGS is thought to be a non-autoimmune inflammatory disorder sparked by gluten that can affect anywhere in the body, but especially the brain and nervous system causing neurological disorders. It can latterly involve reactions auto-immune in nature. For much more on this, see my specialist section.

Gluten intolerance. This is an intolerance (see above) to the gluten which can be found in any or all grains.

Grain intolerance. This is an intolerance (see above) to grains, not necessarily to the gluten or protein fractions.

Wheat allergy – an IgE allergy (see above) to one or several of the proteins in  wheat.

Wheat intolerance – an intolerance, see above, to one or several of the constituents (not necessarily proteins) of wheat. This appears to be most common in relation to highly processed, high-gluten flours and products made from them.

Wheat/Gluten/Grains/Carbs Maldigestion – the problem is not allergy or intolerance-related, more a lack of the digestive enzymes and stomach acid needed to digest them properly. Undigested food can ferment and cause symptoms such as bloating and wind.

All of these conditions are commonly confused.


Dairy / eggs

Strictly speaking, dairy products only refer to cow’s milk products although the term is often taken to refer to all animal milk products (goat, sheep, camel, mare, donkey etc etc)


Are not a dairy product although many people think they are! You can have egg allergy or intolerance as a separate issue though.


Strictly speaking ‘butter’ refers only to churned animal milk but it is used in common parlance in other contexts – cacao/cocoa butter, coconut butter, shea butter, nut butters etc – which have nothing to do with cow’s or animal milk. However, the terminology causes a great deal of confusion amongst those who think they might be dairy/milk/cow’s milk intolerant. Lactose intolerants can usually tolerate butter, which is low in lactose, but a dairy intolerant or dairy allergic usually can’t.


The term should only refer to cow’s milk or at least to animal milks. However, for convenience it is also used in general parlance (not  in ingredients lists or on food labels) for almost any drink which is white(ish) and can be used for similar purposes as cow’s milk eg. soya milk, rice milk, coconut milk, oat milk, spelt milk etc

Nut/Seed/Peanut allergies


Are not tree nuts but legumes – eg. fruits which grow and ripen in a pod – so being peanut allergic does not mean that you will be tree nut allergic or vice versa – although some people can be allergic to both.

Tree nuts

Include  walnut, almond, hazelnut, cashew, pistachio, and Brazil nuts of which cashews, Brazils and hazelnuts are usually thought to cause the most serious allergic reactions. Although coconut are treenuts they are not usually considered to have a high allergy risk.


Pine nuts, pumpkin seeds, sunflower seeds, sesame seeds etc. These are not nuts and, although you can be allergic to any/all of them and you can have both a nut and a seed allergy, the fact that you are allergic to nuts does not mean you will be allergic to seeds and vice versa.



A relatively loose term applied to any product (not only food) that is ‘free of’ whatever it is that you do not want to eat/put on your skin/use on your loo etc.

Those who are intolerant of gluten think it only applies to gluten-free foods, those who have a dairy problem think it only applies to dairy-free foods, those who have multiple allergies/ intolerances think that ‘freefrom foods’ will be free of all of their allergens and get quite upset when they are not!

FreeFrom is not a ‘marque’ and has no legal or regulatory status. There is no governing or policing body for freefrom.

However, the term has been widely adopted by the food industry as a ‘cover all’ term for ‘dietary’ foods that are gluten/wheat/dairy/nut etc free. It is also now starting to be used for foods that are free of other ingredients which are perceived to be unhealthy  (such as additives) and, by extension, even for ‘ethical’ foods – fair trade, organic, low food miles, animal friendly etc.


Phew, told you it was complex, but hopefully that should have helped at least a little. You can find out more on, an excellent resource on all things freefrom.