Can you contract sexual diseases from the same sex?
MD here. It really depends on the disease and type of sex that we're talking about. For instance, if a woman is giving oral sex to another that is HIV positive, there's very little chance of contracting HIV for the woman performing oral sex, unless she has some fresh wounds in her mouth that would allow the virus to enter the blood stream. In case of men it would be slightly different if they are performing anal sex, because it is more likely to have minimal wounds that would allow the virus to enter the blood stream of either partners. As I said in the beginning, the probabilities change depending on the type of sex and the gender of the people involved. In any case, there IS a chance of contracting any STD with whatever gendered partner you have, so no matter what, you should always use protection because there's always a chance (however little) of putting your health and your partners in danger.