I still have red rash on testicles 4 wk i saw a doctor and was told it is a fungal infection. doctor proscribed nystatin it helped a little. advice?

Try other treatment: The most common red rash involving scrotum, groin, etc. is tinea cruris (jock itch), caused by a type of fungus that does not respond to nystatin. Discuss w/ your doctor. Or try an OTC jock itch cream, on the same pharmacy shelves as athletes foot products; look for active ingredient terbenafine or clotrimazole. There are other possible causes; see a dermatologist if OTC treatment doesn't work.