Scarsdale, NY 10583 (914) 472-4100
Westchester Center for Dermatology

Now Seeing Patients Seven Days A Week!

Hablamos Español

Skin Allergy Patch Testing

Published on January 4, 2017

Skin allergies can be quite irritating, and the first step to avoiding an allergy is finding out what you are allergic to. The most common causes for an allergy are mold, pollen, dust mites, dander, and types of foods. Most skin allergies are referred to as dermatitis and show similar symptoms. To understand how skin allergies and patch testing work, we have to understand skin allergies (dermatitis) first.

Types of Dermatitis

There are two main types of dermatitis: allergic contact dermatitis and irritant contact dermatitis. Allergic contact dermatitis is specifically caused when an individual comes in contact with a specific allergen. This could be a substance or a group of related substances. Allergic contact dermatitis is a result of the immune system’s reaction to contact with an allergen. An allergen causes hypersensitivity that then leads to rashes and other symptoms.

In the case of irritant contact dermatitis, the reason for the irritation is typically one that causes inflammation in most individuals if applied at a high enough concentration. It involves the immune system and causes a reaction only when the substance is in contact with the skin.

Patch Testing

Patch testing is a process that helps doctors determine the type of dermatitis a patient has. Patch testing allows doctors to identify the cause of the allergy and differentiate it from other skin conditions. Medications, fragrances, metals, food substances, and more can cause (and in some cases aggravate) dermatitis.

Before patch testing, patients have to sit with their doctors and have a detailed discussion about where the rash started, previous skin diseases and treatments, cosmetics and toiletries being used, and other information. These questions might seem a little intrusive, but they help your doctor identify where the testing should be done and what substances must be tested. It is important for patients to offer full disclosure and not hide anything from their doctor.

After the questions, the doctor will examine the patient’s skin to identify the affected areas. Dermatitis can spread from the initial starting point to other areas around the body through touch and other means. A thorough examination gives your doctor an idea of the substances to test for along with the most common allergens.

To start the actual procedure, your doctor will select an unaffected patch of skin and apply patches held together by adhesive tape. The patches are small aluminum disks that contain the allergens mixed with base substances. Ideally, the patches are placed on the upper back and kept in place for 48 hours. After this time period, the patches are removed.


Once the patches are removed, an initial report is created. 48 hours after the initial report, a final diagnosis takes place. An irritant reaction is evident as soon as the patches are removed, whereas an allergic reaction takes a few days to develop. This is why a second report is taken two days after the initial test. The doctor then scores your test based on international standards and dictates future measures to be taken.

In general, if a patient is reacting to an irritant, that substance can be avoided simply by protecting the skin. Moisturizers and special creams can help. If the patient is reacting to an allergen, then that patient must avoid that substance altogether.

Arrange an Appointment for Testing

With the help of experienced dermatologic surgeon Dr. David Kriegel, you can determine the cause of your allergies and explore effective treatment options. Speak with Dr. Kriegel during a consultation – contact our office to get started.