Why do I have dry skin on my testicles?

Several Causes. The skin over the testicles is the same as any skin. If the oil/sweat glands do not creat enough moisture or protection for the skin, it can be dry. This can occur from excessive washing/harsh soaps, infections (jock itch), irritation from masturbation/clothing, soap left in your clothes, etc. I would start with a moisturizing lotion, 2nd rinse underwear, gentle soap. No better, see your doc.