Researchers at Melbourne University have found that the application of oestrogen to the human penis increased the thickness of the natural keratin layer on the skin, which can prevent HIV infection in men, the PLoS journal reported.

According to them, the epithelium of the human penis is richly supplied with oestrogen receptors, which suggests it could respond to topical oestrogen.

"We have found a new avenue to possibly prevent HIV infection of the penis. Keratin on our skin acts as a barrier to viral infection. We hope to enhance this protection with the use of a naturally, occurring weak oestrogen," Prof Roger Short, who led the study, said.

The Melbourne University team analysed tissue samples from 12 foreskins to make the discovery. Topical oestrogen was applied to the human foreskin for a two-week trial, the result being a rapid and substantial increase in keratin thickness.

"Our study suggested that oestrogen could induce a thickening of the keratin layer of the foreskin epidermis in the same way as it acts in the vagina," said co-researcher

Prof Andrew Pask.