Led by researchers at the University of Melbourne, a study discovered that by applying the female hormone estrogen to the penis, a thickened layer of keratin protein would develop to act as a barrier against the HIV virus. Though it doesn’t protect against other sexually transmitted diseases, the estrogen cream is believed to be a cost-effective method of preventing the spread of HIV.

"By using keratin, we can increase the body's natural defense ... and then the virus can't physically inject itself through that barrier to infect the cells underneath," said Dr. Andrew Pask of the Department of Zoology.

Researchers are hoping that this discovery would also generate interest in circumcision, the process of removing the foreskin of the penis, which offers 80 percent of protection against HIV. The estrogen cream, applied in small amounts to quadruple the keratin layer in the skin, would increase the protection to 100 percent.

For uncircumcised men, the cream would act as a “living condom,” believes Professor Robert Short, lead researcher and member of the university’s Faculty of Medicine, Dentistry and Health Sciences.

"Mathematical models would predict that within say 50 or 60 years that the level of HIV in the world would be significantly reduced as an effect of this," Dr. Pask said.
 
The number is expected to fall if the population took to using the cream or got circumcised.

The study is published in the medical journal PLoS ONE of the Public Library of Science, and the cream will be subjected to clinical trials in Africa.