Human Hair as a Natural Sun Protection Agent: A Quantitative Study

Abstract

The rising incidence of skin cancers attributable to excessive sun exposure has become a major health concern worldwide. While numerous studies have analyzed the sun protective effect of sunscreens, clothing and antioxidants, none to date have measured the photoprotective effect of hair, despite clinical evidence that individuals with balding or thinning hair are at greater risk of skin lesions that can progress to cancer, hence the recommendation to use hats or umbrellas. We analyzed the level of protection offered by hair according to hair density, thickness and color using the spectral transmittance and corrected for relative erythema effectiveness. Our results show that hair provides a barrier against both UVB and UVA radiation which is significantly increased with respect to the hair density, thickness and the presence of melanins. This is the first study to quantify sun protection factor offered by hair, namely hair ultraviolet protection factor (HUPF). We believe that hair should be recognized as an important natural sun barrier in the prevention of UV-induced skin cancers.

3D Modelling for Solar Erythemal UV Protection Provided by Human Hair

“…It confirms that hair is an important natural sun protection means in reducing transmission of UV radiation and should be considered in the prevention of UV-induced cancer of the scalp, particularly among people with alopecia. The effectiveness of the protection depends strongly on the orientation of the head and on the tilt of the hairs and was in line with other epidemiological results [24][25][26].…”

“…Except for a continued use of a headgear, the head is then one of the most sun-exposed anatomical parts, and the real-time exposure is often underestimated. Moreover, strong dissimilarities in the incidence of head and neck melanoma between men and women have been observed in previous researches [24], bringing to the conclusion that hair might have a protective role in sun exposure.…”

“…A dark-skinned person has more melanin molecules in the upper layers of the skin than a light-skinned person [52]. According to [24], approximately 300 hairs cm −3 would be needed to achieve an SPF of 0-10 in the case of brown, blond and red hair, and about 400 hairs cm −3 of white hair. Moreover, it is noteworthy that SPF ratings are calculated for an application thickness of 2 mg cm −2 , which is unrealistic, as most people apply significantly thinner layers.…”

“…The hairs were considered as independent 3D objects, with different alignments and orientations in relation with the solar position, that is, the solar zenith angle (SZA) that represents the angle between the zenith and the line of sight from that point to the sun. To the best of our knowledge, a very small number of studies have tried to quantify the effectiveness of the hair to protect against UV exposure, by spectrometric techniques [24] or dosimetries [25,26], but none of them used 3D modelling methods. Realistic hair modelling is very important for creating virtual humans in computer graphics, but studies are often limited to hairstyling and hair rendering, looking further into the effects of the visible light on the surface of the hair without taking into consideration other spectra, such as the UV wavelengths [27][28][29][30].…”

Exploration of scalp surface lipids reveals squalene peroxide as a potential actor in dandruff condition

“…Our conviction also arises from as-yet unpublished clinical data indicating that increased squalene peroxidation occurs before dandruff becomes clinically visible. UV exposure induces squalene peroxidation on hairless human skin [ 25 ], but only slightly reaches the hair-covered scalp surface [ 8 ]. In addition, in our experience, dandruff incidence tends to be higher in winter than in summer.…”