This condition in most dogs is caused by a large amount of melanin deposition caused by hormones. For dogs, it is a sign of sexual maturity. It usually does not show itching and there is no local redness or swelling. It may also be caused by excessive intake of food and fat. In this case, you need to observe whether there is redness, swelling, pus, local pain, and whether the testicles are abnormally enlarged. If such problems occur, it is recommended to seek medical treatment in time.