Assessment of symptoms, examination of the patient, and certain diagnostic tests are used in the diagnosis of an allergic condition. Although the cause of most allergies is obvious, there are some cases when specific allergens are difficult to pinpoint. In such cases, symptoms are thoroughly screened and the source of the allergen is determined.


These can reveal when the allergy first appeared, in which particular environment it happened, during which season of the year it occurs, and other information relevant to pinpointing the source.


Skin tests are most reliable in verifying allergies to inhaled substances. This is because the skin contains mast cells like those in the nose and lungs which readily react to allergens. The skin prick test, intradermal testing, and patch testing are the three types of skin tests that are widely used.


Although caused by many factors, increased levels of IgE antibodies in the blood may suggest allergies. Blood tests are now being used to identify the antibodies involved in allergic reactions. Radio-allergosorbent test (RAST) and multiple allergosorbent test (MAST) are common types of blood tests used in diagnosing allergies.


When the cause of the allergy is left undetermined even after skin tests, the suspected allergen is placed directly on the organ that shows allergic symptoms. These tests include Nasal Challenge, Bronchial Challenge, and Oral Challenge Tests(Food).


The Peak Expiratory Volume (PEV) and the Peak Expiratory Flow Rate(PEFR) are the two most commonly used lung function tests. These are very useful in diagnosing asthma and in monitoring its conditions.


A bowel biopsy is carried out to confirm a suspected food allergy in infant colitis and to diagnose coeliac disease. Confirmation of celiac disease is extremely important as the only treatment for it is complete avoidance of gluten through a strict gluten-free diet.

The accurate diagnosis of an allergy is very important. Only when it is properly diagnosed can there be improvement in health conditions. In some cases, a cure can even be found.