Abstract

A topic individuals are those who develop an allergic reaction on exposure to certain foreign substances, allergens. For each individual these allergens are specific. They can act in minute concentration to cause common diseases such as allergic asthma and allergic rhinitis. Skin testing can identify atopic individuals, but it cannot be relied on to indicate the allergens causing respiratory symptoms. Skin tests may be positive for allergens which are not causing symptoms (for example, house dust and grass pollens) and occasionally negative for those which do.