From the Guidelines
Dermatologists can perform allergy testing, specifically patch testing, to identify contact allergies that cause skin reactions like rashes or dermatitis. This involves applying potential allergens to the skin (usually on the back) under patches for 48 hours, then examining for reactions at 48 and 96 hours, with a sensitivity and specificity of between 70% and 80% 1. Common allergens tested include metals, fragrances, preservatives, and medications. Some key points to consider when performing patch testing include:
- The standard method involves the application of antigen to the skin at standardized concentrations in an appropriate vehicle and under occlusion 1.
- Various application systems are available, of which the most commonly used are Finn chambers 1.
- Preprepared tests are significantly more reliable than operator-prepared tests 1. For more comprehensive allergy testing, such as blood tests or skin prick tests for food allergies, environmental allergies, or systemic allergic reactions, patients are usually referred to allergists/immunologists who specialize in these conditions. Dermatologists focus on patch testing because contact dermatitis directly affects the skin, which is their area of expertise, while allergists have broader training in all types of allergic reactions throughout the body. It's also worth noting that photopatch testing may be carried out where photoallergic contact dermatitis is suspected, with the recommended method involving the application of a photoallergen series and any suspected patient materials, in duplicate, on either side of the upper back 1. However, the incidence of true photoallergy in suspected cases is low, at < 5% 1. In terms of referral guidelines, allergist-immunologists are specifically trained to diagnose contact dermatitis and more allergist-immunologists than dermatologists currently perform patch testing, but dermatologists can still play a crucial role in the diagnosis and management of contact dermatitis 1.
From the Research
Dermatology and Allergy Testing
- Dermatologists do perform allergy testing, particularly for skin-related allergies [ 2, 3 ].
- The most frequently used allergy test in dermatology is patch testing, which is used to diagnose allergic contact dermatitis [ 2, 3 ].
- Patch testing involves applying small amounts of potential allergens to the skin and observing the reaction [ 2, 3 ].
Types of Allergy Testing
- There are two types of skin testing used in clinical practice: percutaneous testing (prick or puncture) and intracutaneous testing (intradermal) [ 4, 5 ].
- Prick testing involves introducing a needle into the upper layers of the skin through a drop of allergen extract [ 4, 5 ].
- Intracutaneous testing involves injecting a small amount of allergen into the dermis [ 4, 5 ].