Contact Dermatitis and Patch Testing: Reviewing the Patient Experience

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Allergic contact dermatitis (ACD) is a type IV hypersensitivity reaction characterized by T-cell mediated eczematous eruptions upon exposure to allergens on the skin to which one has become sensitized. Patch testing remains the most important tool in the evaluation of suspected ACD. Since the US Food and Drug Administration approved the use of the Thin-layer Rapid Use Epicutaneous (T.R.U.E.) test in 1997, many dermatologists and allergists have utilized it as a first-line tool and refer for more comprehensive testing when a relevant allergen is not identified or was missed. Although most patients report satisfaction with patch testing and improvement in their skin conditions, less than half recall their relevant allergens 6 months after testing, even with relatively few (1 to 2) positives.^1,2 The actual rate of patient satisfaction and recall of allergens is likely lower as many of these reports are from patch test specialty clinics and do not include those tested with the T.R.U.E. test or those lost to follow-up.

As a whole, the importance of relationship-centered care during the patch testing process is well documented.^3,4 Because the primary treatment for ACD is allergen avoidance, patient education and follow-up after diagnosis is key because the onus is on the patient to successfully avoid the problem allergens.⁵ For dermatologists in a busy practice, these conversations can be time consuming and sometimes overwhelming for patients, especially those who have more ubiquitous and difficult to avoid allergens such as fragrance or those that are occupationally related.

Here, we offer a review of the patch testing process from the lead author’s perspective as a current contact dermatitis research fellow years after initial exposure to patch testing and diagnosis of ACD as a patient at the same center.

The Patch Testing Process

Although the T.R.U.E. test is often utilized as a first-line tool, it is important to note that it is only believed to identify a clinically relevant allergen(s) in as low as 25.5% of patients who have ACD.⁶ Even for allergens included in the limited test, relevant reactions to fragrances, rubber accelerators, and formaldehyde in particular are likely to be missed when compared to the same allergens dispersed in petrolatum applied utilizing Finn Chambers.⁷ As such, comprehensive testing is recommended to minimize the need for repeated testing.

Comprehensive patch testing is resource intensive for both physicians and patients. A 5-to 7-day commitment with restrictions on movement and bathing to preserve the integrity of the test is no small ask. In addition, it is important to consider that many patients indicated for patch testing have long histories of failed treatment with several specialists, which may result in them entering the patch testing process with a baseline of frustration. Taking a moment to pause, empathize with, and affirm the patient’s experience before proceeding is beneficial.

At the start of the process, dermatologists should provide patients with basic information about the pathophysiology of ACD, indications for patch testing, and how delayed-type reactions differ from the traditional immediate-type allergies they may be more familiar with (seasonal allergies, food allergies, and “eczema”), necessitating a week-long test rather than the single office visit for prick testing.^8,9 It should also be stressed that only reactions present on the final day of testing are considered true allergies.

Whenever possible, testing patient’s own personal care products in addition to the standardized allergens should be considered. Testing the products that patients are most frequently in contact with is necessary to make confident determinations of clinical significance.¹⁰ This becomes critical when ascribing clinical relevance to results in patients who demonstrate several borderline (“doubtful” or “+/-”) reactions. Further, directly testing products that the patient is suspicious of instills confidence in the process.

During the testing week itself, most patients report itching and sleep difficulty, positively correlated in intensity with the number of positive patch test reactions.¹¹ A reminder that antihistamines will not interfere with the results of patch testing may alleviate some of these stressors. Additionally, reiterating that exposure to their contact allergens will not result in anaphylaxis like traditional immediate-type allergies can help put some patients’ minds at ease.

Allergen Avoidance Counseling

It has been demonstrated that patients with ACD who successfully recall and avoid their relevant allergens have improvement in their quality of life; however, up to 50% have difficulty doing so.^2,12 This gap in care can be addressed with appropriate counseling and follow-up, especially for patients who have many relevant positive reactions.

Studies have demonstrated a wide range of patient perception of success in allergen avoidance, from 50% to as high as 90%. Patient rating of satisfaction in allergen counseling has been less volatile, from 62.9% to 80%.^1,2,5,13 Differing practices at patch test centers likely play a role in these variabilities and emphasize the importance of proper counseling at the conclusion of the patch testing process.

While useful as an initial tool, the allergen information handouts provided with the T.R.U.E. test can often leave patients confused if not combined with counseling from the dermatologist. Beyond discussing the basics of the allergen (what it is, where it can be found), dermatologists or knowledgeable staff should review personal care products with the patient to identify which products may contain the culprit allergens. Together, the patient and clinician can categorize these into products that should be avoided and those that can be continued safely. From our experience, when this process is not completed with patients, many continue to be exposed to their sensitivities unknowingly.

Inevitably, key products in patients’ routines will be stopped during this process. It can be easy for patients to feel overwhelmed, especially if their allergens are more ubiquitous in common personal care products. Although some allergens are listed “as-is” on ingredient labels (e.g., methylisothiazolinone), some have numerous alternative names and cross-reactors (e.g., formaldehyde and formaldehyde releasers) that can be tricky even for experienced patch testing staff to recall, let alone for the patient new to allergen avoidance. As such, recommending safe alternatives is a key responsibility for the patch testing physician.

The efficacy of a written shopping list for patients who have skin care product ingredient allergies has been demonstrated.¹⁴ For patch testing, utilizing apps such as the American Contact Dermatitis Society’s Contact Allergen Management Program or the Mayo Clinic’s SkinSAFE is critical to create personal safe lists on which patients can base future personal care product use. Keeping in mind that 40% of patients rely on social media to learn about safe products, use of these databases can be a source of more reliable information.

For patients who have all-negative results, it is just as important to have a clear plan for follow-up. Due to the similarities of several eczematous conditions both visibly and under the microscope, ruling out ACD can be a significant advancement in care, even if it may not feel like it in the moment with only negative results after undergoing a week of testing. Notably, it has been shown that quality of life is improved in patients after patch testing even in these cases.¹⁵ This may be due, in part, to the exclusion of ACD, leading to a different diagnosis with follow-up.

“Now What?” Living With Contact Dermatitis

The effects of ACD on patient emotions and quality of life are well documented in the literature.^16-18 Immediately following the final patch visit (and relief from the first shower) comes the shopping process for new personal care products to replace the ones deemed to be unsafe. This period can feel uncomfortable for many patients. Even with the aid of apps, it is easy for patients to feel overwhelmed while in the store aisles, cross-referencing each individual brand of deodorant to find one that exactly matches the safe list.

During the final patch testing visit and subsequent follow-up visits, dermatologists are uniquely positioned to have an impact on how patients will think about their sensitivities and ultimately interact with their environment. This positive impact may be through the simple recommendation of preparing a list of cross-referenced products before going to the store. For those with a greater burden of ACD, patch testing physicians may consider hosting support group sessions to provide a safe space for their patients to converse with others sharing the same experience. As an example, our clinic hosts a monthly support group for patients with ACD, which is received positively and has many members that have attended for several years.

In some cases, patients may continue to feel overwhelmed by their sensitivities years after the patch testing process. Every instance of contact with the environment has the potential to remind those with ACD of their allergies and the repercussions of a flare if they are not careful, which can weigh heavily on patients’ minds, especially those with strong sensitization to allergens that may be less avoidable. This constant vigilance can have a negative effect on patients’ mental health and their ability to lead a fulfilling life. Each patient will have a different threshold of tolerance for active dermatitis and can strive to find their own balance between constant allergen avoidance and living with occasional flares. With the aid of an attentive dermatologist, patients can be empowered to navigate new product regimens and feel confident in their ability to manage their ACD.

Puneet Arora is a fourth-year medical student at the University of Minnesota Medical School in Minneapolis, MN, completing a research fellowship in patch testing at the Park Nicollet Contact Dermatitis Clinic. Dr Hylwa is a faculty physician in the department of dermatology at Hennepin Healthcare and Park Nicollet Contact Dermatitis Clinic and an assistant professor at the University of Minnesota in Minneapolis, MN. Disclosure: The authors report no relevant financial relationships.

References:

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