How do a man gets brush burns on the side of his penis after intercourse?

Sexual Intercourse: Most of these sexual encounter rashes or sores are from friction and are not sexually transmitted diseases. If there is not enough lube in your vagina or if during the sexual encounter there was a lot of masturbation of your partner then friction may be the culprit for this outcome. These friction caused lesions should heal very quickly with out complication. But, lube or extra lube may help.