Ari M. Goldminz, MD, Talks Patch Testing Pearls at AAD Meeting

NEW YORK— Patch testing has the ability to help patients in a variety of ways and can provide a successful roadmap for solving challenging cases, said Ari M. Goldminz, MD, instructor at Harvard Medical School and associate physician at Brigham and Women’s Hospital, at the 2019 American Academy of Dermatology Summer Meeting.¹

Initially described in the late nineteenth century by German physician Joseph Jadassohn², patch testing can help inform specific product recommendations, reduce treatment requirements, crack difficult cases, and most importantly, improve patients’ quality of life. During his meeting session, Dr Goldminz discussed some tips for practitioners referring their patients for patch testing.

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General principles for patch testing, Dr Goldminz said, include identifying patients’ allergens, avoiding culprits, and improving patients’ dermatitis. Among the pearls he shared were:

Knowing available options for allergy testing and the answers each option can provide is a good place to start. In addition to the assessment of delayed type IV hypersensitivity reactions through patch testing, immediate type I hypersensitivity reactions evaluated with skin prick testing can also play a role.

“Sometimes, it’s not so clear-cut in the sense that a patient has just type I hypersensitivity or just type IV hypersensitivity. For certain patients, it can be helpful to undergo both types of allergy testing depending on their presenting symptoms and history,” Dr Goldminz said. Patients with eye symptoms due to environmental allergies, such as pollen, may introduce contact allergens to the same area in the form of antihistamine eye drops or nail polish, for example.

In addition, a Repeat Open Application Test (ROAT) or use test is a simple tool that can assess for sensitivity to a topical leave-on product such as a lotion or cream. This test involves twice-daily application of a leave-on product typically on the crease of the arm for 2 weeks and is considered positive if pruritus and/or dermatitis appear at the application site. For topical corticosteroids, the test is performed on the abdomen or thigh for up to 4 weeks. He also discussed contact urticaria testing, photo patch testing, and options for testing with more unusual contact allergens.

Dr Goldminz highlighted a key message regarding a patient’s experience. “One fundamental of patch testing is communication, because it is important that we prepare our patients for all of the steps involved during and after testing, as well as the considerable amount of new information that will be provided through the process” he explained.

There are also a number of special scenarios to keep in mind when thinking about patch testing, Dr Goldminz emphasized. Although ideally patients would be off immunosuppressive treatments during patch testing, for various reasons this may not be practical. For example, some patients may be taking immunosuppressant medications to prevent organ transplant rejection or others may have severe, widespread dermatitis that would flare if tapered off their treatments.

Dr Goldminz also added that patch testing is performed in children, but is typically avoided in women who are pregnant or breastfeeding.

The period after patch testing is very important, during which time utilization of a stepwise approach is helpful, according to Dr Goldminz. It can take at least 3 to 4 weeks to see significant improvements with allergen avoidance. If a patient’s condition does not improve, potential considerations could include factors such as non-adherence to allergen avoidance recommendations, inadvertent allergen exposure, unidentified allergens, and alternative diagnoses.

In addition to a thorough investigation of the possible explanations for limited improvement after patch testing and allergen avoidance, alternative therapeutic options beyond topicals can also be considered when indicated, said Dr Goldminz. Some of these treatments might include prednisone, cyclosporine, phototherapy, methotrexate, mycophenolate, mofetil, azathioprine, or biologics.

Finally, do not lose sight of mimickers and secondary diagnoses. Further workup with studies such as a KOH or oil prep, direct immunofluorescence, or culture can be helpful in certain cases, Dr Goldminz said. Atypical manifestations of contact allergy can also be seen, so for some challenging cases with an unclear diagnosis, it can be helpful to keep allergic contact dermatitis somewhere in the differential diagnosis, he added.

—Christina Vogt

References:

1. Goldminz AM. Patch testing: pearls for the referring practitioner. Presented at: American Academy of Dermatology 2019 Summer Meeting; July 25, 2019; New York, NY. https://www.aad.org/scientificsessions/sam2019/SessionDetails.aspx?id=12760.

2. Lazzarini R, Duarte I, Lindmayer Ferreira A. Patch testing. An Bras Dermatol. 2013; 88(6): 879-888. doi:10.1590/abd1806-4841.20132323.