What you guys describe is a typical:
a) STD - can be (from female transferred) yeast infection
b) fungal infection (athletes foot)
antifungal gels (metronidazole gel) or creams (Zalain, mycozan, clotrymazole, nyzoral, lamysil) can help with it, but the treatment should by systemic. You need to complete the course of the therapy otherwise it will come back in an aggravated state.)
Do not use shower gels for that matter as they contain lots of softeners and moisturizers - a bar of antibacterial soap will do you good. After shower dry the area completely (even using a hair dryer to eliminate any moist as it gives a perfect environment for the bacteria to thrive, and you can even put a couple of Cleanex tissues between your thigh and scrotum on both sides. That will keep the area dry and prevent bacteria from spreading.