I believe that few owners will deliberately observe the color changes of the dog’s nipples, but to a certain extent, changes in the dog’s nipples can also indicate changes in the dog’s physical condition at this time. Regular observation will help us determine whether there is anything abnormal about the dog.

1. Local stimulation

External factors can irritate your dog’s nipples, just like other parts of your dog. This condition often results in discoloration of one or several nipples. For dogs who like to rub against carpets or blankets, the friction may cause trauma to their nipples, causing pain. Licking or scratching due to skin conditions or contact allergies can also cause localized reactions and discoloration of the nipples.

2. Changes in body hormones

The most common cause of nipple discoloration is hormonal changes in unneutered female dogs. If your dog has not been neutered and his breasts become red and enlarged, and he gains weight and an enlarged belly, you should consider whether he is pregnant. These changes occur in the second trimester of a dog's pregnancy, usually around day 40 of pregnancy. It is important to note that pseudopregnancy can also cause similar symptoms. If you cannot make a good judgment, you need to send it to the hospital for testing to help judge.

3. Caused by breastfeeding of female dogs

If the female dog is lactating, the puppies will often suck and bite the nipples, which may cause local irritation. Moreover, puppies' nails may scratch the nipples, allowing bacteria to enter the skin and cause mastitis. Therefore, pay more attention to changes in the female dog’s nipples. Be sure to pay close attention to swelling, warmth, red breast tissue, and other accompanying disease symptoms.

4. Breast tumors

If a dog suffers from mammary gland tumors, its breasts will become firm and have nodular masses. This is a common disease in female dogs. When you touch the mass, it will feel like particles under the skin. The skin of the breast may become ulcerated or infected, and the nipple may be swollen, red, and may have fluid discharge. Don’t think that male dogs will not suffer from such diseases. Although the probability is relatively low, they are also likely to develop the disease. If you find something abnormal and you cannot judge it yourself, it is best to go to the hospital for a check-up.