Justin Bieber gives tips for sun damage

Teenagers who copied his hairstyle, with the hair falling across the forehead, had a big difference in the skin of their forehead and of the face.

The skin under their bangs of hair was paler and it had almost no freckles, while freckles covered the rest of the face.

"Freckles themselves are not harmful, but they are markers of sun damage, and are linked to an increased risk of melanoma (skin cancer) in adults," Bernard Cohen, from Johns Hopkins University in the US, was quoted as saying.

The team called this approach the "big bang theory", and realised they can teach kids about skin damage due to sunlight using this example.

They found it "a gimmicky way to make them smile and engage them in a conversation about sun protection", Cohen said.

Despite the protective effect of the bangs seen in some patients, teens with the hairstyle should not, however, rely just on bangs for sun protection, Cohen added.

The study was published in the journal JAMA Pediatrics.