A zoologist in Melbourne has discovered that rubbing estrogen on the tip of a human penis causes the "keratin layer" of skin to thicken, which may prevent the spread of HIV:

Dr Andrew Pask from the Department of Zoology at the University of Melbourne analysed the tissue samples from 12 foreskins and made the discovery.

"This 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 Dr Pask.

"Keratin on our skin acts a barrier to viral infection. We hope to be able to enhance this protection with the use of a naturally occurring, weak oestrogen," said Professor Roger Short of the Faculty of Medicine, Dentistry and Health Sciences who lead the research.

To confirm its effect, topical oestrogen was applied to the human foreskin for a two week trial. This resulted in a rapid and substantial increase in keratin thickness.