The word allergy is derived from the Greek words meaning “altered reaction” and an allergic individual usually suffers physical symptoms (e.g. headache, vomiting, rashes, migraine, asthma, etc.) when exposed to substances to which he/she is sensitive. The substance, which provokes this reaction, is called the allergen. It can be house dust, dog dander, foods, chemicals or even bacteria, just to name a few.
Over the past few years, there has been increasing awareness of many diseases and complaints that can be caused, or contributed to, by the presence of allergies.
Allergies are quite common. Over 20% of the population is allergic to something. However, when one considers symptoms such as hay fever, wheezy bronchitis in children, minor degrees of eczema and food intolerance, the true incidence of allergy and/or intolerance to one or more environmental agents would certainly be much higher.
Types of Reactions:
Immediate Food Reaction As the name implies, this food reaction can occur within 3 hours after digestion. The reaction is caused by the presence of a high IgE antibody level in the blood, which sets off an immediate allergic response. Symptoms can be rashes after eating an apple or headache after drinking wine.
Delayed Food Reaction Delayed food reactions can occur up to several days after ingestion of the reactive food, making it difficult to link one’s symptom to the food eaten several days ago. Such hidden allergies are often the cause of many “chronic symptoms.” The immune response to delayed food reactions are often caused by antibodies other than IgE. They are IgG, IgA, IgM and IgD. These antibodies combine with the food particles in the blood to form “immune complexes” which cause inflammatory reactions in tissues. Such inflammatory reactions can occur in any part of the body, thus producing many kinds of symptoms such as headache, eczema, joint pain, mental disorders, etc.
Diagnosis of Food Allergies Obviously immediate food reaction can be identified easily. However, delayed food reactions are much more difficult to diagnose. According to recent research, IgE antibodies cause immediate food reactions. Delayed food reactions are often associated with IgG4, a subclass of the whole IgG molecule. At Meridian Valley Laboratory, our food allergy test uses a combination IgE and IgG4 protocol. The test can detect both IgE and/or IgG4 allergic reactions. Thus both immediate and delayed food reactions can be detected.