He had a vasectomy four years ago. Dear Patti Thanks for your question. I assume your husband does not have a fungal infection of the inner thighs and scrotum like jock itch. This can be diagnosed by a rash of the affected skin. Scrotal itching is a common symptom of a fungal infection or contact dermatitis especially when the environment is warm.
Contact dermatitis is an allergic reaction of the skin to some substance.
Heat generated under the bed clothes causes the scrotum to sweat and thus increases scrotum irritation. If no rash is present, I would try a drying talc, like baby powder. If a rash is present you may try a medicated antifungal powder, cream or spray. If this does not help, you a may try a different detergent for your laundry. Sleeping without underwear may also help the sweat to evaporate more easily.