Allergy Patch Testing
Allergy patch testing is a dermatological procedure that determines whether a patient's skin rash is caused or aggravated by an allergy to substances that come into contact with the skin.
This testing requires additional time, effort, and expertise to perform.
Performed at Kelsey-Seybold's Memorial Villages Campus, allergy patch testing is used to evaluate more than 80 contact allergens. In fact, we are one of the few facilities in the Houston area that offers comprehensive patch testing in our clinics, without our patients having to wait months for an appointment.
A wide variety of potential dermatitis-causing allergens are applied to adhesive patches, which are placed on your back or arm. Some common trigger substances are dyes, fragrances, metals, and preservatives in personal care products such as soap, shampoo, or conditioner.
The patches are worn for three days (72 hours) and are removed when you return to the doctor. The skin under the patches is then evaluated for irritation, which may indicate an allergy. You’ll be asked to return in another 48 hours to see if there is a delayed allergic reaction to any of the substances.
With patch testing, it's expected that you will experience skin reddening and itching at several testing sites. This indicates a positive result. However, there are some risks and side effects of patch testing that may include:
- Blistering at sites with positive results
- A reaction that may continue for up to a month
- Eczema at the testing sites, for those who have had eczema in the past
- An increase or decrease in the pigment of the skin where patches are placed, which may last for months or permanently
- An infection at the testing sites (rare)
It's important to note that patch testing only detects allergens that cause contact dermatitis. It doesn’t diagnose any other types of allergies, such as food allergies. Learn about other types of allergy testing at Kelsey-Seybold.
Reasons for Patch Testing
If you suffer from dermatitis, needle (or skin prick) testing isn’t likely to determine whether allergens are causing the rash or inflammation. Patch testing, however, can more accurately detect whether a contact allergy is to blame, particularly in cases where the allergy takes several days to cause a reaction.
Patch testing can detect allergic reactions to more than 80 substances that are regularly in contact with the skin. Some of the most common allergens are:
- Cosmetics ingredients
- Leather chemicals
Who’s a Candidate for Patch Testing?
Patients who are most likely the best candidates for patch testing are those who have had recurrent rashes or other reactions on their skin to substances with which they regularly come into contact (also known as contact dermatitis). Patients of any age can undergo patch testing safely.