My husband keeps getting a reoccuring rash thing in his private area in the creases, it doesn't itch, but smells really bad and is red. What can it be?

Fungal infection. Fungal infections often develop in dark moist areas of the body such as the groin area and under the arms and breasts. He can try an over the counter anti-fungal treatment for a few days but if the rash doesn't improve, he needs to see a doctor.