Pigmented contact dermatitis and hair dyes: A retrospective case–control multicentre study in Korea

Abstract

BackgroundPigmented contact dermatitis (PCD), a rare variant of non‐eczematous contact dermatitis, is clinically characterized by sudden‐onset brown or grey pigmentation on the face and neck. It is hypothesized to be caused by repeated contact with low levels of allergens.ObjectivesThis study evaluated the risk of using hair dyes in patients with PCD in Korea.MethodsA total of 1033 PCD patients and 1366 controls from 31 university hospitals were retrospectively recruited. We collected and analysed the data from the patient group, diagnosed through typical clinical findings of PCD and the control group, which comprised age/sex‐matched patients who visited the participating hospitals with pre‐existing skin diseases other than current allergic disease or PCD.ResultsMelasma and photosensitivity were significantly more common in the control group, and a history of contact dermatitis was more common in the PCD group. There were significantly more Fitzpatrick skin type V participants in the PCD group than in the control group. There was no significant difference in sunscreen use between the groups. Using dermatologic medical history, Fitzpatrick skin type and sunscreen use as covariates, we showed that hair dye use carried a higher PCD risk (odds ratio [OR] before adjustment: 2.06, confidence interval [CI]: 1.60–2.65; OR after adjustment: 2.74, CI: 1.88–4.00). Moreover, henna users had a higher risk of PCD (OR before adjustment: 5.51, CI: 4.07–7.47; OR after adjustment: 7.02, CI: 4.59–10.74), indicating a significant increase in the risk of PCD with henna dye use. Contact dermatitis history was more prevalent in henna users than in those using other hair dyes in the PCD group (17.23% vs. 11.55%).ConclusionHair dye use is a risk factor for PCD. The risk significantly increased when henna hair dye was used by those with a history of contact dermatitis.

Intriguing concept of pigmented contact dermatitis: Further understanding the role of hair colours including natural henna

“…Importantly, in the study by Kim Y.C. et al, 3 the odds of hair colour usage in patients having PCD was found to be 2.1–2.7, and that of using henna was found to be 5.5–7, as compared to controls, depending upon unadjusted and adjusted analysis, respectively. The most important derivation in clinical context is association discussed with henna usage, as this is the most commonly used natural alternative for PPD allergies and also PCD.…”

“…In the present issue of the JEADV, Kim Y.C. et al present compelling data from a substantial number of PCD patients ( n = 1033) and controls ( n = 1366) in a case–control study shedding light on significant associations with hair colour usage among patients having PCD 3 …”

“…Importantly, switching from a non‐henna dye to henna dye, or the number of subjects who had used both non‐henna and henna dyes was not particularly evaluated, which could have added even more value to the current results and can be further performed in a prospectively designed observational study. Notably, missing data regarding use of hair colour and sunscreens, particularly evident in the cases could have affected the results 3 . Another factor leading to association could be henna contamination, which Kim Y.C.…”

“…The association between henna and PCD could be a significant confounding factor in the present study 3 as majority of the patients having PCD, especially those with a history suggestive of contact dermatitis to hair colours, are advised to use plain red henna (preferably compounded at home using dried henna leaves in order to avoid contamination with paraphenylenediamine [PPD]). This usage would show up in a case–control study, essentially meaning an association, but not a causation/ risk factor per se because of the inherent limitation of a case–control study design which can capture only associations.…”

“…When tested as is, the rate of positivity with ‘non‐henna’ dyes was significantly higher than ‘henna’ dyes (71 vs. 48%, respectively). Rates of positivity with pure henna 10% solution could have been added to results 3 …”