When you have a cold, your nose runs and you might have a sore throat but your vagina doesn’t leak. On the other hand, when you have a vaginal infection, your vagina will leak but your nose won’t. I offer these examples to show you that different microbes live in different parts of your body. Colds are caused by rhinoviruses, and they live in your nose, and travel down into your throat, and so when you have a cold your mucus and saliva are full of rhinoviruses but they’re not anywhere else. So kissing can and will spread them to you, and he’s right to protect you, but having sex is somewhat safe. I say somewhat for a couple of reasons. First of all a man touches his penis when he urinates, so he could put some microbes that were on his hands onto his penis. (There won’t be any viruses in his ejaculate but they can live on his skin for a short time.) And if he touches his hands to his nose and then touches your face with his hands, or touches your hands and you touch your face, you’re also likely going to catch his cold. So it’s probably better to keep some distance from each other altogether. But if you keep the physical contact to a minimum, and wash his penis ahead of time, you won’t automatically catch his cold performing oral sex on him. .