Skin test

The usefulness of the test in diagnosis of food allergy is limited. in intra dermal test minute quantities of extracts containing suspected antigens are packed into the skin over the arm. in scratch test a small amount of the solution containing the antigen is placed into a series of scratches made into the skin. in patch test the antigen is applied to a piece of filter paper over the skin and covered with cellophane and kept for 24 hours. if a red inflammation or hive like wheal appears at the site of contact,the food is suspected to contain the allergen, sometimes oedema or erythema due to vasodilation is seen