J Clin Aesthet Dermatol. 2024;17(6):55–57.
by Lynn Nguyen, BS; Lily Parker, BS; Kerry Hennessy, MD; Nirav Shah, MD; and George Cohen, MD
Ms. Nguyen and Parker are with the Morsani College of Medicine at University of South Florida in Tampa, Florida. Drs. Shah, Cohen, and Hennessy are with the Department of Dermatology and Cutaneous Surgery at Morsani College of Medicine at University of South Florida in Tampa, Florida.
ABSTRACT: Patch testing is the standard diagnostic test used for patients presenting with symptoms of allergic contact dermatitis. The grading of patch test results classically varies from 1 to 3. The assessment of these results begins with a visual inspection of the presence of erythema, vesiculation, and induration. This leads to a subjectivity in visual evaluation of a patch test. Positive patch testing results can present differently in patients with darker skin tones. A greater variety of images of allergic contact dermatitis in patients with darker skin phototypes can better guide the diagnosis of this condition in skin of color. People with darker phototypes are historically underrepresented in dermatologic images and texts; thus, identifying erythema in darker phototypes may be more difficult for dermatologists, whether or not they were trained in areas of decreased phototype diversity. In this article, we present positive patch testing findings on several different phototypes, with the intention of contributing to images of phototypes underrepresented in dermatology literature. Keywords: Patch testing, skin of color, allergic contact dermatitis, contact dermatitis, allergy testing, erythema
Allergic contact dermatitis (ACD) is a condition that affects about 20 percent of the general population in the United States (US).1 Patch testing is the gold standard for diagnosing ACD and identifying triggers in patients.2 According to the US Census Bureau, non-White individuals, including Black (13.6%) and Latinx (19.1%) individuals comprise a notable portion of the US population.3 However, these populations are underrepresented in patch testing data compared to White individuals. A 2018 review by DeKoven et al4 showed that only about 4.8 percent of Black and 2 percent of Latinx patients were represented in patch testing data from North America. Based on the limited availability of patch testing data from patients with skin of color, there are inadequate clinical images demonstrating patch testing in this population. This is concerning, since dermatological conditions may vary in presentation based on skin pigmentation,5 so ACD may go underdiagnosed in patients with skin of color. To address this, we provide a series of images of patch testing reactions in the skin of White and Black patients to illustrate various clinical presentations.
Patch testing is the gold standard for diagnosing ACD. The grading of patch test results classically varies from 1 to 3. The assessment of these results begins with a visual inspection of the presence of erythema, vesiculation, and induration. Next, a determination of whether the findings represent an irritant or an allergic contact reaction is made. Finally, it is decided whether allergic reactions are clinically relevant to the patient at the time of evaluation. However, the assessment of patch tests is affected by subjectivity, particularly involving the inspection and palpation of the test area and the interpreting clinician’s background knowledge and experience. Combined with the aforementioned paucity of patch testing data and clinical images from patients with skin of color, this can lead to difficulty in evaluating patch testing results in these patients.
In patients with deep pigmentation of skin, or those who would have historically been categorized as Fitzpatrick Skin Types V and VI, erythema is especially difficult to detect. Many erythematous diseases, such as pityriasis rosea, psoriasis, and eczema might have a different presentation based on skin phototype. We have found that when grading patch test reactions in patients with skin of color, erythema may not be present, and its absence may lead to misdiagnosis. This case series illustrates the variety of positive patch test reactions in people with skin of color and how lack of erythema is not synonymous with a negative result. All patients discussed in this paper presented with an itchy, recurrent rash.
Case series
Case 1. Figure 1 depicts a 40-year-old female patient with skin phototype II who demonstrated a positive reaction to patch testing with edematous weals noted in the affected patch sites. This picture may be used as a reference for a standard positive result in White patients.
Case 2. Figure 2 depicts a 46-year-old female patient with skin phototype I with positive patch testing.
Case 3. Figure 3 depicts a 51-year-old male patient with skin phototype IV and a 2+ positive reaction. Although erythema is difficult to detect, palpability and vesiculation are additional clues to positivity. Two images of the same patient’s patch testing sites in different lighting are provided to better visualize the cutaneous changes.
Case 4. Figure 4 depicts a 62-year-old male patient with phototype II skin exhibiting all false positive reactions to patch testing with “angry back syndrome” in the affected patch sites. “Angry back syndrome” refers to when hyperreactive skin appears following patch testing and causes hyperreactivity at other sites, commonly leading to false positive patch test interpretations.7
Case 5. Figure 5 depicts a 54-year-old male patient with phototype V skin and a false positive reaction to patch testing in the affected sites.
Case 6. Figure 6 depicts a 39-year-old male patient with phototype V skin and probable false positive reaction to patch testing with post-inflammatory hyperpigmentation (PIH) in the affected patch sites. PIH is marked by increased melanocytic activity in response to inflammation or injury of the skin.8 It occurs in all skin types, but it is more prevalent in people with skin of color or Fitzpatrick Skin Types III to VI. While PIH appears in about 25 percent of White patients, it manifests in about 48 percent of Latinx patients and about 65 percent of Black patients.8
Conclusion
The scarcity of clinical images that demonstrate results of patch testing in patients with skin of color and the subjectivity inherent in the interpretation of patch test results may lead to an underdiagnosis of ACD in this population. This contributes to health disparities associated with persistent ACD that disproportionately affect patients with skin of color. In this case series, we provide images of positive and false positive patch testing results as well as post-patch testing reactions in the skin of White and Black patients. With this, we hope to contribute to clinical knowledge and enable physicians to better recognize, diagnose, and manage ACD in patients with skin of color.
References
- Tamazian S, Oboite M, Treat JR. Patch testing in skin of color: A brief report. Pediatr Dermatol. 2021;38(4):952–953.
- Fonacier L. A Practical Guide to Patch Testing. J Allergy Clin Immunol Pract. 2015;3(5):669–675.
- United States Census Bureau. Quick Facts: United States. Accessed May 8, 2024. Available at: https://www.census.gov/quickfacts/fact/table/US/PST045221.
- DeKoven JG, Warshaw EM, Zug KA, et al. North American Contact Dermatitis Group Patch Test Results: 2015-2016. Dermatitis. 2018;29(6):297–309.
- Kelly AP, Taylor SC, Lim HW, et al. Taylor and Kelly’s dermatology for skin of color, 2nd edn. New York, NY: McGraw-Hill Education LLC; 2016.
- GA Johnston. Standardization of patch tests and the doctors who read them. Br J Dermatol. 2009 Sep;161(3):493–495.
- Mitchell JC. The angry back syndrome: eczema creates eczema. Contact Dermatitis.1975;1(4):193–194.
- Anvery N, Christensen RE, Dirr MA. Management of post-inflammatory hyperpigmentation in skin of color: A short review. J Cosmet Dermatol. 2022;21(5):1837–1840.