A small study published in AIDS, January 21, 2010. Researchers at the Division of Infectious Diseases, Department of Medicine, Chicago, Illinois, USA, examined the foreskins removed by circumcision of 16 men. The researchers found that there was no significant differences in the thickness of the keratin layers of the inner foreskin and the outer skin. The authors concluded: "Keratin layers alone are unlikely to explain why uncircumcised men are at higher risk for HIV infection."