South Korea: Findings from a retrospective case-control multicentre study in Korea revealed that using hair dye is a risk factor for pigmented contact dermatitis (PCD).
Furthermore, when henna hair dye was used by people with a history of contact dermatitis, a significant increase in the risk was seen in the study published in the Journal of the European Academy of Dermatology and Venereology.
Pigmented contact dermatitis is a rare variant of non-eczematous contact dermatitis. Its clinical characteristics include sudden-onset brown or grey pigmentation on the neck and face. It is hypothesized to be caused by repeated contact with low allergens levels. Myoung Shin Kim, Sanggye Paik Hospital, School of Medicine, Inje University, Seoul, South Korea, and colleagues evaluated the risk of using hair dyes in patients with pigmented contact dermatitis in Korea.

For this purpose, the researchers retrospectively recruited a total of 1033 PCD patients and 1366 controls from 31 university hospitals. They collected and analyzed the data from the patient group, diagnosed through PCD's typical clinical findings and the control group. The control group comprised age/sex-matched patients who visited the participating hospitals with pre-existing skin diseases other than current allergic disease or PCD.
The authors reported the following findings:
Melasma 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, it was revealed that hair dye use carried a higher PCD risk (odds ratio [OR] before adjustment: 2.06; OR after adjustment: 2.74).
Henna users had a higher risk of PCD (OR before adjustment: 5.51; OR after adjustment: 7.02), 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%).
"Our findings revealed that using hair dye is a risk factor for pigmented contact dermatitis," the researchers wrote. "A significant increase in the risk was seen when henna hair dye was used by those with a history of contact dermatitis."
Reference:
Kim, M. S., Chung, B. Y., Chang, S. E., Oh, S. H., Ryu, H. J., Kim, D. H., Lee, J. H., Ko, J. Y., Kim, J. E., Lee, J. H., Lee, G. Y., Jeon, J., Choi, H., Roh, M. R., Bae, J. M., Na, I., Jung, H. J., Bang, C. H., Kim, H. S., . . . Kim, Y. C. Pigmented contact dermatitis and hair dyes: A retrospective case–control multicentre study in Korea. Journal of the European Academy of Dermatology and Venereology. https://doi.org/10.1111/jdv.19395