Hypersensitivity Reactions

Hypersensitivity Reactions
Many people have uncomfortable reactions to various foods, and this is often considered to be due to food additives and other artificial chemicals such as pesticide residues, rather than to the food itself.

This discomfort is usually called allergy by nonmedical persons, but there are also nurses and doctors who use the term allergy when they mean various kinds of untoward reactions to foods without knowing the mechanisms of such reactions.

Strictly, an allergy is a harmful physiological reaction reaction caused by an immunologic mechanism.

If the mechanism is not allergic one but the reaction resembles allergic reaction, the term intolerance is often used.

The symptoms mimic those seen in allergic reactions, but the amount of agent producing the reaction is small enough not to cause a toxic reaction.

When the mechanism is not known, it is better to talk about hypersensitivity, which can mean both allergic and intolerance.

There are several foods and food additive that can cause both immunologic and non immunologic reactions indistinguishable form each other.

For example, fish can act both as nonspecific histamine liberators and as true allergen.

Tuna, mackerel and certain cheeses contain histidine and tyrosine to such an extent that histamine and tyramine produced by decarboxylation from them can cause allergic type symptoms in atopic people.

Among food additives, cinnamon and nitrogen mustard are the most well-known cause of both allergic and nonallergic reactions.

Terminology of Hypersensitivity Reactions
Hypersensitivity
A small amount of a substance produces symptoms that can be objectively verified and repeated.

Allergy
Immunologic mechanism are involved in the pathogenesis of symptoms.

Atopic allergy
The reaction is mediated by immunoglobulin E.

Intolerance
A small amount of substance produces a reaction similar to or closely resembling a true allergic reaction, but immunologic mechanisms not involved.

Hypersensitivity Reactions