Allergen solution. Fingers holding a vial of food colourings allergen solution for use in the allergy testing of children. The solution may be used in a patch test for allergic contact dermatitis. In the test, a small amount of each potential allergen is put onto a patch which is placed onto the skin. Allergic contact dermatitis is indicated by any areas of inflamed skin, the position of the inflammation denoting the allergens to which the patient is sensitised. Although some allergic conditions may be alleviated by drugs, usually diet or behaviour is altered to lessen exposure to the allergens.