Well my girl friend does experience the same thing after intercourse especially when I ejaculate in her. What I noticed was my diet. When ever I ate a lot of oily foods and we had intercourse she did get lots of pimples, when I reduce oily and fatty food, her pimples does reduce after intercourse.I believe there's a link because when a sperms gets into the vagina most of them are absorbed by the walls of the vagina into the body of the woman. The sperms contain lots of proteins and other nutrients. So what ever he carries in his blood is transferred into his semen and is also transferred to you. I haven't asked any doctor why but my guess is ask your man to change his diet and see if it occurs. Also let the doctor test his blood to check for any unusual or too much oil in the blood.

Hope this helps.