Hair gives little sun protection for scalp

Friday, 12 September 2008 Anna SallehABC

Sun visors may keep the sun off your face, but what about your scalp?

A full head of hair provides surprisingly low protection for your scalp from the sun, Australian researchers warn.

Physicist Associate Professor Alfio Parisi and colleagues, from the University of Southern Queensland in Toowoomba, report their findings in the journal Photochemistry and Photobiology.

The researchers say a significant number of melanomas occur on the scalp, with one study showing they make up 13% of melanomas. "So the question arose how UV penetrates through the hair," says Parisi. Parisi and colleagues studied how much ultraviolet (UV) radiation from the sun got through to the scalp with a full head of hair. They placed a UV sensor in the centre of the top of the head of a mannequin adorned with a wig made of human hair. The researchers then tested how much UV got through when the sun was at different positions in the sky.

"It started about 9 o'clock in the morning right through to lunch time," says Parisi.

He and colleagues also tested what happened when the head was upright or tilted towards the sun, and what happened under the shade of a beach umbrella. They also tested the impact of grey and brown hair, and short (4.9 centimetres) and long (10.9 centimetres) hair. Short hair may have an edge They found that the colour of the hair made no difference, but that short hair may provide marginally more protection than long hair. Parisi thinks this is because long hair weighs itself down at the part and exposes more of the scalp to sun.

Overall, the researchers found hair offered a protection factor ranging from 5 to 17, which is significantly lower that the average sunscreen, which offers a protection factor of 30.

"This is much lower than properly applied sunscreen," says Parisi. "I'm surprised that the protection factor is so low."

While previous studies have measured hair's ability to protect the top of the ears, Parisi says this is the first study to measure its ability to protect the scalp.
"People who are going to be outside for a long period of time - even if they've got a full head of hair - should really wear a hat," says Parisi, warning that sun visors, and even caps, allow parts of the head to be exposed to the sun.

The Australian Bureau of Statistics reports that an estimated 1.2 million Australians work outdoors and there are more than 300 occupations that require mainly outdoor work.

A previous study found that outdoor workers are exposed to 5 to 10 times more UV radiation than other workers. "Males are twice as likely to die from melanoma, in all likelihood because of the higher rate of men in outdoor jobs," say Parisi and colleagues.