Suggest Treatment For White Patch On The Head Of Penis

hello my boyfriend and I have recently just started having sex. We are both STD free and we dont use condoms. We noticed he had a dry patch of skin under the head of his penis that only seems to get bigger and he claims it burns after we have sex. we have tried lotions and everything and nothing seems to work. Could he be allergic to my vaginal secretions or do you think it is something more?