Can a Woman's Finger Length Predict Susceptibility to Acne Vulgaris?

What can the length of a woman’s fingers tell us about their susceptibility to acne vulgaris (AV)? Plenty, it turns out, according to a study in the American Journal of Clinical Dermatology. The study suggests that a more masculine second-to-fourth digit (2D:4D) ratio may predict sebum levels and, therefore, the potential for developing AV.

It is well-established that the 2D:4D ratio is a record of how much exposure people had to androgens, such as testosterone, in the womb. Put simply, the longer the ring finger is compared to the index finger, the more masculine traits an individual may display. The ratio has been used in research regarding human sexuality, aggression, and physical prowess, among others. Clinical research has suggested that lower sperm counts and increased risk for heart disease and obesity in males is associated with high digit ratio. Low digit ratio, however, is associated with increased rate of ADHD and autism in males, and a reduced risk of eating disorders in both men and women.

Development of the digits and the sebaceous glands both occur during the same gestational period; therefore, the association between the 2D:4D ratios and AV may result from the effects of the prenatal endocrine environment on the sebaceous glands. This isn’t the first study to look at the relationship between 2D:4D ratios and acne. In fact, the same authors established the connection in a 2014 study in the Journal of the European Academy of Dermatology and Venereology. The older study found that 2D:4D ratios of female patients with AV were significantly lower than healthy females in both hands, but found no significant difference between male acne cases and controls. Acne severity was positively correlated with the left 2D:4D ratios and mean 2D:4D ratio, whereas the duration of acne was negatively correlated with the right 2D:4D ratios in females.

The newer study followed up on this work to help determine why this connection exists. The study analyzed 215 females with AV and 92 healthy controls. Finger-length measurements were made using a digital Vernier caliper, and the sebum levels of five facial areas were measured. Acne severity was assessed using the International Consensus Conference on Acne Classification System.

The 2D:4D ratios of the patients with AV were significantly lower than those of the controls, for both hands. While acne severity was positively correlated with skin sebum levels, no correlation between acne severity and 2D:4D ratios was observed. Potential future areas of study include whether there are any corresponding predictors of male AV. Yet to be studied is the impact of the finger ration on treatment and length of time with the condition.