The Artuvetrin® Skin Test determines which substances a dog is allergic to, by injecting small amounts of different allergens into the skin (subcutaneously). It is then possible to evaluate whether or not a local reaction has developed at the injection site. Before carrying out the skin test, any medication that might affect the results (including prednisone, cyclosporin and antihistamine) must be discontinued for 2–6 weeks. The skin test is carried out on the lateral thorax of the patient after carefully shaving a patch of hair. A small quantity (0.05 ml) of histamine and saline (positive and negative controls) plus solutions of the chosen allergens are injected into the skin at different locations. After 15–20 minutes, all injection sites are assessed for skin swelling (wheal formation). If there is allergy to a certain substance, an inflammatory reaction will appear on the skin, visible as a swelling. The extent of this swelling is compared to that of the positive and negative controls, allowing identification of the substances to which the patient is allergic. A single patient may be allergic to many substances.