Skin tests in food allergy are not of much help; it is the history of the patient which is of greatest help. Other procedures that help are elimination diets. The patient is instructed to note in a diary all the food taken and the symptoms produced,if any. By studying these reports for two to three weeks, the doctor can often detect the onset of symptoms after a new type of food, or after repeated intake of a certain food. The elimination of these foods, one at a time, should result in disappearance of the symptoms. This is followed by controlled intentional ingestion to confirm the allergy. The difficulty arises when the offending food is either milk, egg or wheat, which are common ingredients of many other foods and therefore its presence may not be suspected by the patient.Food allergy is more common in children than in adults. Recurrent abdominal upsets, skin rashes and unrelieved cough should be suspected of having an allergic basis. Proper diagnosis can lead to very favourable results.*40\260\8*
Chemical Mediators Causing Symptoms of Allergic Rhinitis
Mediator Symptoms Produced
Histamine Stuffy nose, runny nose, sneezing, itchy nose,
itchy throat, itchy palate, itchy ears
Prostaglandin D2 Inflammation of nose
Leukotrienes Runny nose, stuffy nose, inflammation
Each of these mediators exerts its effect by interacting with a receptor on the surface of a specific cell in the nasal tissue. Histamine, for example, binds to one of two types of receptors, called H1 and H2 receptors. Tissue that doesn’t contain either of these receptors cannot be acted upon by histamine. It is mainly through the H1 receptor that histamine stimulates tissues in your nose and causes allergic symptoms. Antihistamines and other medications used to treat allergic symptoms act by blocking the receptors through which the chemical mediators work. Thus, antihistamines work mainly by blocking the interaction of histamine with the H1 receptor.