Skin testing is a standard diagnostic tool used to identify the specific allergens that trigger contact dermatitis and, occasionally, systemic allergic reactions. Common trigger substances include cleaning solutions, detergents, cosmetics, perfumes, latex rubber, and poison ivy.
Skin allergy tests may be administered to diagnose the root causes of allergic reactions. Only penicillin and certain related medication allergies are commonly tested for in this manner, however, since the risk of a systemic reaction to food substances or other drugs is considered to be too great.
Types of Skin Test Procedures
Before undergoing allergy skin testing, patients should stop using corticosteroids in the area to be tested and avoid taking oral antihistamines since either may produce inaccurate results. Allergy skin tests using potential irritants, such as pollen, insect venom or animal dander, are administered in three primary ways.
Scratch Tests
Scratch tests are administered on the forearm. Once the targeted area has been cleaned with alcohol, a drop of each potential allergen is applied to a particular place on the forearm, marked to indicate its presence. The substance is applied where the outer layer of skin, the epidermis, has been pricked. Frequently, the scratch test administered is a T.R.U.E. TEST®, a comprehensive exam which tests for sensitivity to 29 common allergens.
Patch tests
In this method of allergy testing, several patches are taped to the skin, usually the skin of the upper back. Unlike the two previous methods of allergy skin testing, patch tests necessitate that the patches be left in place for 48 hours during which the area must be kept dry. As with the other forms of allergy skin testing, patients must be alerted to the possibility of a severe reaction so they can remove any patch that is causing serious problems, such as wheezing, and notify their physician immediately.
No matter which way the allergens are applied to the skin, the physician examines the area for a reaction, which may range from completely negative (meaning the patient has no allergy to the substance) to extreme (where the patient shows a severe reaction to the substance. Once positive results have been determined, patients can take steps to avoid their triggers and prevent allergic responses from occurring.
Side-Effects of Allergy Skin Testing
Although skin allergy testing is considered a safe and efficient diagnostic tool, these tests do cause a small area of contact dermatitis at the site of application, and may, under certain circumstances, result in a mild version of systemic reactions. In very rare instances, skin allergy tests, usually only intradermal ones, can cause anaphylaxis, a systemic reaction during which the patient may experience itching, wheezing, swelling of the face or entire body, trouble breathing, and low blood pressure. Since this type of reaction can result in shock and even death, in a short time, patients showing symptoms of anaphylaxis require emergency treatment.
For more information about allergy skin testing or to get started on your individual test, contact Laserderm Dermatology & Cosmetic Laser Surgery and schedule a consultation.