A damp smelly scrotum can be due to physiological causes such as tension, or it can be due to disease. For example, chronic prostatitis, scrotal eczema, hyperthyroidism, etc. If the symptom is the only one, it is usually considered to be physiological, but if it is accompanied by other discomforts such as scrotal itching, weakness and weight loss, it is considered to be caused by a disease.