Patch test for contact dermatitis and allergens from biomedical devices


Patch tests can be very helpful in determining the source of the rash in patients with suspected allergic contact dermatitis (ACD). However, clinicians must learn to know when and in what cases to use this very useful diagnosis. tool.

Allergic contact dermatitis can occur at any age, and current conventional wisdom is that in general, anyone with recurrent or persistent dermatitis suspected of having a component of ACD should have a patch test. There are a multitude of potential causes of DCA which can often be due to a variety of ingredients in personal care products used by patients.

“The typical consumer can apply over 30 pounds of personal care products to her skin per year, and while the average adult woman applies 12 personal care products per day – exposing her to 168 discrete chemicals – the average man uses 6 personal care products a day with 85 unique new ingredients, ”said Luz S. Fonacier, MD, past president of the American College of Allergy, Asthma & Immunology (ACAAI), professor of medicine, New York University (NYU) Long Island School of Medicine, and Head of Allergy and Training Program Director, NYU Langone Hospital-Long Island, who recently spoke at the ACAAI Annual Scientific Meeting held November 4-8 in New Orleans, Louisiana.1 “These chemicals and ingredients can potentially be the cause of ACD and as such should be properly investigated and patch tested if suspected.”

An accurate history of personal care product use is also crucial in uncovering the potential source of CDA. According to Fonacier, many patients empirically modify the products they use on the affected area of ​​CDA assuming that if the dermatitis persists, the products stopped were not the cause. However, the new product is likely to contain the same allergen as the original. Fonacier stressed that a detailed history and careful monitoring of the products used or disposed of are very important in locating the source of ACD.

Although clues to the cause of ACD can be suspected from the distribution on the hands, face and feet, he said that up to 20% of ACD cases manifest as generalized rashes. or scattered, which further underlines the diagnostic importance of patch tests. According to Fonacier, patch testing should be considered in patients with chronic eczematous dermatitis, persistent or recalcitrant dermatitis, occupational dermatitis, dermatitis of the hands, legs or feet, stasis dermatitis, AD that does not occur. not improving, facial dermatitis (eyelid) and dermatitis with unusual distribution.

“It’s important to carefully eliminate false positives and false negatives when reading results, however, you also don’t want to overinterpret the results,” Fonacier said. “Once you have your positives, you need to determine the relevance of the result to the patient’s symptoms, history and exposure.”

Once allergens have been identified from a patch test, patients should review their personal products and discard those that contain the allergens tested. This process can be very difficult and intimidating for patients, Fonacier said, which could lead to compliance issues regarding allergen avoidance.

Databases generating a list of allergens to avoid, as well as a comprehensive list of skin care products that are free of their identified allergens, increase patient compliance and can lead to faster resolution of the condition. clinical disease. According to Fonacier, the cycle of an ideal patch test procedure involves identifying allergens, determining relevance, educating patients, and then offering them treatment and management alternatives.

To help improve allergy prevention compliance, there are currently 2 computer-generated databases available in the United States that list allergen-free products that the patient is allergic to and can safely use, including the Contact Allergen Management Program (CAMP) available to members of the American Contact Dermatitis Society, and the Mayo Clinic Contact the Allergen Replacement Database (MENU).2.3

Hypersensitivity reactions to orthopedic implants exist and remain a controversial area in contact dermatitis and patch testing. Unfortunately, the value of patch testing and the clarity of diagnosis that can be achieved is not fully recognized in all specialties, he explained.

“One of the main challenges with patch testing today is that many orthopedic surgeons still fail to recognize that hypersensitivity to metal implants can lead to joint replacement failure, and that patch testing can be helpful in identifying hypersensitivities. allergic to metal prostheses. Some orthopedic surgeons have learned that an allergic reaction to implants constitutes less than 1% of joint failure cases, or that patch tests do not reflect the joint’s immune system and therefore [it] can’t be trusted. The standard of care must change so that all clinicians understand the diagnostic value of patch tests under the right circumstances, ”said Karin Pacheco, MD, MSPH, assistant professor in the Department of Medicine, Division of Environmental and Environmental Sciences. Occupational Health, National Jewish Health, Denver, Colorado, who spoke at the ACAAI meeting.

An allergic reaction to an implanted metal can range from a mild irritation or rash on the implant to pain and tenderness in or around the implant. In severe cases, an implanted joint can loosen and become unstable. A system-wide rash is rare.

Current orthopedic literature deals with what to do with joint failure, Pacheco said, but the 10% rate of joint replacement failure hasn’t changed much over the past 20 years. Common causes that an orthopedic surgeon will consider are infection or improper position of the device. However, according to Pacheco, it is important to recognize that sensitization to implant components is another important cause of joint failure.

“The patients we see are referred by their orthopedic surgeon and have already been assessed for possible infections or mechanical problems and, in this context, our rates of relevant patch test results are high with around half of our patients showing sensitization. to something in their joint, ”Pacheco said. “So it’s important to consider the diagnosis, do the right patch test, and then correlate the results with the actual components of the implant. ”

Interestingly, most orthopedic implant manufacturers’ websites do not list the makeup of implants, making it even more difficult to find the potential source of its allergic hypersensitivity.

The majority of orthopedic implants are made of cobalt chrome with a small amount of nickel and have undergone extensive research and development resulting in very good mechanical properties, she said. If ACD is suspected, clinicians should investigate whether the patient is sensitized to anything in the composition of the common implant, and then clarify if they are sensitized to anything in their specific implant. For this, clinicians should use a standardized panel that incorporates all the metals included in different implants today, as it could contain the answers to these important questions.

For preoperative patients, it is reasonable to test those with a history of reactions to metallic or methacrylate products such as artificial nails. Still, most patients without a history of allergic reactions are usually not tested before the initial implant, she said, because without it the results would be difficult to interpret.

“We not only need to publish more articles demonstrating that in the right patient, patch tests can make a huge difference in their results, but we also need to involve other specialties and emphasize the diagnostic importance and benefits of the tests. epicutaneous in the right scenarios, ”said Pacheco.


Fonacier and Pacheco did not report any relevant disclosure.

The references:

1. Fonacier LS, Pacheco K. Pearls and the pitfall of patch tests for contact dermatitis and allergens from biomedical devices. Presented at the 2021 ACAAI Annual Scientific Meeting; from November 4 to 8, 2021; in New Orleans, LA, and virtual.

2. Contact the Allergen Management Program. American Contact Dermatitis Society. Accessed November 3, 2021.

3. Contact the Allergen Replacement Database. Mayo Clinic. Accessed November 3, 2021.


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