patch testing

When Patch Testing can Help

patch testingEczema can be a challenging and frustrating condition. One of the many subsets of eczema is contact dermatitis, a form of eczema that occurs from the skin coming in contact with certain substances. When your dermatologist suspects that something in your environment could be contributing to, or causing the flare he or she may consider patch testing.

What is a patch test?

Patch testing is a method of testing a substance on the skin to determine if someone will experience a reaction to that substance. The aim of the patch test is to find potential triggers for irritant dermatitis or contact dermatitis. The dermatologist usually takes a detailed medical history from the patient, and then determines which substances should be tested.

How is a patch test performed?

On the day of testing, it may be easiest to wear loose-fitting clothing that buttons in front. The person’s back or inner thighs are usually marked with pen, to indicate which substance has been applied to each location. Then the substance is applied and covered with a patch for a period of time, typically 48 hours. The patches shouldn’t get wet, so sponge bathing is usually advised instead of regular baths or showers.

After the patches have been in place for the specified amount of time, the doctor will remove them and examine the skin. The results will be interpreted two to four days after removing the patches, then again between five and seven days. The test won’t work if the patches loosen or fall off.

What are some reasons a dermatologist might recommend a patch test?

* When the eczema first appears in adulthood.

* For chronic eczema that isn’t responding to adherent treatment, which means the patient isn’t following the treatment exactly as prescribed.

* When there may be substances in the workplace that could be contributing to the condition.

* When a refill is prescribed for topical corticosteroid or systemic therapy, such as oral steroids, or oral immunosuppressive drugs.

What substances can be tested?

Dyes, fragrances and resins can be tested. Although many types of skin care products can also be tested, those that are meant to be rinsed off such as shampoos and body cleansers can’t be tested because they’re likely to cause an irritant response, which means they would likely irritate the skin as they are not intended to be left on the skin.

How can I get patch tested?

A dermatologist will assess the patient’s condition, and then decide if patch testing is appropriate. You can ask your dermatologist if patch testing might be helpful for you condition.

Note: Eczema Society of Canada always recommends that you work with your doctor and/or dermatologist to find a treatment course that is right for you and specific to your needs.

Source: Dr. Susan Nedorost – Lecture at American Academy of Dermatology Annual Meeting, March 2014, Denver.

For more information please visit Eczema Society of Canada at