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Sometimes it doesn’t seem to matter what it is; allergy, intolerance, whatever, you feel awful after eating it. Or think you do. Or you’re definitely convinced that something you eat is making you ill, but pinning down exactly what is tricky, since there’s no pattern between what you eat and how you feel.
So, let’s start off, at least, by defining what we’re talking about here .
An allergy assumes an adverse reaction in which the immune system is involved (in scientific terms, when the IgE antibody is released in response to a protein introduced to the body). Essentially, the immune system rejects the food, or some component of it. The reaction can be of devastating severity, for example, anaphylaxis. Generally speaking, food allergies have the following characteristics
• a small number of foods result in a reaction
• they are not eaten frequently
• the reaction appears within two hours of consuming the food
• The digestive system, airways and skin are most likely to be affected, and they respond by becoming inflamed.
• small amounts of food can lead to a significant reaction
• Allergies are fixed and permanent.
Allergies occur when the surface membranes are unusually sensitive to substances, or when a barrier, such as the skin, is breached. Diagnosis of an allergy may include the use of skin prick tests and blood tests such as ELISA and RAST, but can only be confirmed by an elimination-reintroduction diet.
False Food Allergies produce symptoms very similar to those of allergies, but the mechanism involved in the production of excess histamine is different (the IgE antibody is not over stimulated).
Hidden Food Allergies occur when an individual is sufficiently sensitive to an allergen that it may make them slightly ill, but constant exposure to the substance makes this reaction less severe. Avoiding the substance results in an improvement in health, but when the substance is reintroduced there may be a dramatic reaction.
A food intolerance will result in an adverse reaction, however the immune system is not involved in the process Instead, the body produces an idiosyncratic response to a food, or a part of a food. There are many causes of food intolerances; for example, lactose intolerance is a metabolic dysfunction, due to a lack of the digestive enzyme lactase, and results in excess gas, bloating, and pain in those who suffer from it. It is estimated that 11% of the UK adult population is lactose intolerant (compared with 85% of the world’s population; drinking cow’s milk is very much a western habit). Milk Intolerance, on the other hand, simply suggests that the individual has some sort of reaction to consuming milk, which does not involve digestive enzymes: it is a pharmacological reaction. The reaction produced by an intolerance is generally slower and less violent than the reactions caused by allergies. Food intolerances may have the following characteristics:
• a number of foods may be involved
• they are commonly eaten
• the reaction appears anything up to three days later
• any part of the body can be involved
• ceasing to eat the food may result in withdrawal symptoms
• reactions may be proportional to the amount of the food eaten
• Intolerances may change over time
The use of the IgG antibody to diagnose an intolerance is being researched. Only one journal, Gut, has so far done any research into this. Using a double blind study they concluded that 25% of patients benefited from cutting out foods that produced an IgG reaction. However, food intolerances can only be clearly diagnosed using an elimination-reaction diet, and, because of the propensity of food intolerances to involve more than one food, and take time to show symptoms, they can be very tricky to diagnose. Temporary food intolerances may be the result of severe flu or gastric upset.
Food Sensitivity is a blanket term, which covers both food allergies and food intolerances. A food which you are sensitive to may cause an allergic reaction. It may simply produce symptoms of intolerance or, in some cases; both allergy and intolerance may be involved. A sensitivity can be described as an exaggeration of a normal side effect; for example, the headaches some people experience after consumption of a small amount of alcohol.
Food Aversion is used to describe a psychologically based dislike and avoidance of certain foods; for example, a bad experience of salmonella may result in an aversion to chicken. Food aversion is not covered in depth by this site, but those suffering from aversions may find helpful substitution suggestions.
Doctors are more likely to define whether a food is causing an allergy or an intolerance based on the symptoms produced by it. For example, eczema is not traditionally accepted as an allergenic symptom.