Inflammation: Individuals with darker skin more prone to chronic subclinical irritation

October 1, 2009

A recent study showed that individuals with darker skin appear to have greater chronic subclinical inflammation in the stratum corneum, compared to those with lighter skin.

Key Points

This increase in subclinical cutaneous chronic inflammation may translate into a higher risk for developing some dermatoses, and, according to an expert, precautionary measures may be useful in order to stem this potentially troublesome predisposition.

"We are still at the beginning of understanding what the differences are between skin that has more melanin and less melanin in it. However, there are very likely some functional differences between the two," says Alexa Boer Kimball, M.D., department of dermatology, Harvard Medical School, and co-author of the study.

"These differences may not just be related to how the skin deals with UV exposure, but also how it deals with other skin damage resulting from other environmental insults. Whether the damage is acute or chronic may matter, as well," she says.

Clinical evaluation

Dr. Kimball and colleagues conducted a clinical study evaluating the difference in the extent of chronic subclinical inflammation in dark-complexioned individuals compared to light-complexioned ones. To assess skin inflammation, noninvasive tape-stripping samples were taken from the cheek area (adjacent to the nasolabial folds) in a total of 55 women with normal skin, of whom 44 and 11 had a light complexion (Fitzpatrick skin type II-III) and a dark complexion (Fitzpatrick skin types IV-V), respectively. Proteins were extracted from the tape strips and analyzed for the cytokines IL-IA and IL-I Receptor Antagonist (IL-IRA), using ELISA as well as total protein content to normalized cytokine recovery.

Results showed that the levels of the inflammatory biomarker IL-IA in dark skin were significantly higher than those in lighter skin, suggesting that dark-skinned individuals have a greater chronic subclinical inflammation compared to light-skinned individuals. Also, the skin auto-inflammatory biomarker (IL-IRA) content was found to be much lower in dark-skinned participants compared to age-matched light-skinned participants. According to Dr. Kimball, this means that darker patients appear to have less of a capacity to down-regulate chronic subclinical inflammation compared to light-skinned patients.

"I believe that these results add to the evidence that there are some biological differences between the Fitzpatrick skin types that go beyond simply the melanin distribution, although, ultimately, they may be related in some way. Our results suggest that darker skin types may have a higher risk of developing some dermatoses," Dr. Kimball says.

According to Dr. Kimball, physicians should be made aware of this increased risk in their darker-skinned patients and possibly try to modify their topical treatments in order to stem the subclinical inflammation present in their skin. Some patient populations tend to use products that are more ointment-based or more emolliating, possibly because these patients feel this subclinical inflammation, to some extent.

Dr. Kimball suggests that a simple change in the maintenance regimen in dark-complexioned patients may be of benefit, as well as possibly starting them on topical anti-inflammatory or antioxidant approaches. Topical corticosteroids could also be employed; however, these should be reserved for clinically evident inflammatory processes, she says.

Disclosures: Dr. Kimball is a consultant for Johnson and Johnson.