Dermatology patch testing

There are no appointments on Tuesdays and Thursdays. You may shower and apply deodorant the morning of your first appointment. You may NOT shower or bathe again until after your last appointment on Friday. The doctor will evaluate your skin, and the nurses will place the patches on your back, possibly the upper arms. On average we test to over substances. The patches are removed from your back, and the initial interpretation is recorded, 48 hours into the test.

The doctor reads the final results of the test, 96 hours into the test, and reviews the results with you at this visit. A positive patch test will be red, raised, and itchy possibly lasting several weeks. Sometimes the skin will blister resulting in discoloration over the area on your back that may take time to fade. Access myPennMedicine For Patients and Visitors. Find a Program or Service. Allergic Contact Dermatitis.

Knowing what the offending allergens are, will help you know what to avoid and can help in the treatment of your condition. The underlying cause of some rashes may be difficult to identify with patch testing, however, it offers a good chance to identify what might be the cause of the rash.

Patch testing itself is NOT therapeutic, meaning that the process of patch testing will not improve your rash directly. It is the identification and future avoidance of offending allergens that offers the opportunity for improvement in your rash.

Patch testing itself usually occurs over three visits. You will receive additional information, such as what medications to avoid, modifications you may need to make to your daily routine including bathing , and what to expect once the results of your patch tests are received.

You will receive counseling on ways to avoid ongoing exposure to your recently identified allergens, and you will be given a list of products which are safe for continued use.

Patch Testing. Get to the Source of Your Allergies Many substances that come in contact with the skin can cause an immune system reaction called allergic contact dermatitis.

What are Some Common Allergens? There are over known allergens, many of which are found frequently in our daily lives, including: Plants - poison ivy, oak and sumac, as well as common plants such as chrysanthemums. Toiletries — cosmetics, perfumes, shampoo, soaps, lotions, or other skin care products. Patch testing is largely of value in determining the cause of allergic contact dermatitis, and is not useful in investigating irritant dermatitis.

Patch testing has some limited value in investigating some types of drug allergy , and a specialised type of patch testing is used for investigating photo contact allergy photopatch testing. No visible redness or swelling means contact allergy to that product is unlikely. Some highly irritant products cannot safely be repeat open or occluded patch tested, as they may require appropriate dilution. Patch tests are not the same as skin prick tests , which are used to diagnose hay fever allergy.

A series of allergens are applied, usually to the back, on special tapes fitted with small aluminium discs Finn chambers that hold the individual allergens between 10 and Anywhere between 30 and over a hundred allergens can be applied at a time. Ideally the patch tests are applied when the dermatitis is inactive, but if the back skin is inflamed, the arms or abdominal skin can be used for application. After carefully marking the position of the patch test panels, they are removed at 48 hours, and the skin inspected 48 hours after that.

Antihistamines can be taken as normal as they do not interfere with the type IV hypersensitivity reaction. There are several thousand potential contact allergens, but some are much more common than others.

A standard series of allergens at least will usually be applied. The composition of the series varies over time and from country to country, as different allergens may become more or less important. At a pre-patch test consultation, the series of allergens required are selected. This is important so that potential allergens are not missed, and any product dilution arranged. It is helpful to bring health and safety data sheets and product packaging which may list individual allergen ingredients.

If there is a suspicious product that may be the cause of dermatitis, it is important this is brought along to the doctors appointment. Patch testing may be required and its packaging will contain valuable details of its constituents. Some allergens are coloured and will temporarily stain the skin PPD is black, disperse blue is blue, textile resins are a variety of colours.