Hello and hope you are doing well.
Up to 20% of the population perceive themselves as suffering from food allergy but only 1-2% of adults have genuine food allergies. The most common culprits are peanuts, milk, eggs, soya and shellfish. Allergic reactions are mediated by IgE antibodies, which are released on exposure to a particular allergen. These in turn activate mast cells and lead to a local response or systemic anaphylaxis. The diagnosis of allergy is difficult to prove or refute. Clinical suspicion and trial of elimination diets are used. An allergy specialist might be able to help by identifying the allergen and by desensitizing.
Hope this helped and do keep us posted.
Thanks for your reply. The route of desensitisation may not be open to my wife as the reaction is so severe. In one instance last year she ate one potato crisp and was ill for days afterwards. It would help if our family doctor acknowledged that there might be a problem - he has not heard of such an intolerance, and therefore assumes that it does not exist. We will be pointing him toward this site!
One of the major problems we have is that garlic is sometimes not listed among food ingredients. Shopping, with great care, can take some time and considerable care.