It's Fungus or yeast infection....common around skin folds like thighs and genitals.. avoid sweating, sharing clothes,towels and soap.. specific medicine required depends on the severity.. for detailed prescription do direct online consultation by sending photos.

Vaginal itching after sex that only happens on occasion is probably nothing to worry about. Not enough lubrication during intercourse or too much friction could cause vaginal itching. If this is the case, symptoms will probably improve by simply avoiding sex for a few days. If symptoms persist or you experience other symptoms, an allergic reaction, vaginal dryness, or an STD may be the cause. Consult a Dermatologist for the same to prevent further aggravation.