A study into the protective value of the hair on human heads has revealed that short hair shields the underlying scalp from ultraviolet (UV) radiation better than long hair.
Researchers from the University of Southern Queensland measured the amount of solar UV radiation able to penetrate to the skin on the scalp through both short and long hair. They compared the conditions of a human head in full sun and under shade; then that of a head tilted towards the sun in full sunlight. The amount of UV radiation reaching the scalp beneath the hair was compared to that reaching a bald scalp.
The study was performed on head-forms with a sensor placed at the centre of the scalp. These were covered with hairpieces made from both brown and grey coloured human hair. It is expected that red and blonde tones would provide protective properties similar to the grey hair, though further study is required to confirm this.
The results determined that short hair provided greater protection from UV radiation than longer hair. The believed reason behind this is the fall of the hair. While short hair tends to stand on end, longer hair has more parting which exposes a larger area of scalp skin to sunlight. Brown hair also reduced the penetration of sunlight in contrast to grey hair; this is presumed due to greater reflective or absorptive properties of the brown hair.
The most notable finding from the study was that none of the hair-styles or colours provided a great deal of protection. The ultraviolet protection factor (UPF) of the various colours and styles ranged from 5 to 17, signifying that between 5 and 20% of UV radiation still reaches the scalp. This indicates that significant damage to the scalp can occur even over short periods of UV exposure. Such results may go a long way towards debunking the common myth that a full head of hair protects against UV.
The research has significant implications for workplace health and safety in Australia and is particularly relevant for employees who are outside for short time frames where scalp protection may not previously have been deemed necessary. Previous research shows that up to 13% of all melanomas, the most lethal form of skin cancer, occur on the scalp. Hence, the consequences for insufficient protection can be severe. The authors recommend that outdoor workers regularly seek shade and wear broad-rimmed hats with rear flaps to more adequately protect the skin on the scalp from UV damage.
Reference
Parisi, A.V, 2009, ‘Solar ultraviolet protection provided by human head hair’, Photochemistry and Photobiology, 85(1):250-254.
Image reference
‘Antje’s hair’ uploaded to flickr.com by ‘quinn.anya’ on the 26 January 2008, <http://www.flickr.com/photos/quinnanya/2223387584/>.
