Mastitis

Mastitis is inflammation of one or more mammary glands, most commonly seen in female dogs and cats during lactation or in the period shortly after weaning. The affected gland may become swollen, warm, firm, or discoloured, and milk expressed from it can appear abnormal—thickened, bloodstained, or otherwise changed in appearance. Owners often notice these changes when a nursing mother seems uncomfortable, when puppies or kittens appear restless or are not gaining weight as expected, or when routine handling reveals a gland that feels different from the others. Mastitis can range from mild localised changes that resolve with supportive measures to more significant inflammation that affects the mother's comfort and the offspring's ability to feed. In some cases, signs may extend beyond the gland itself—the nursing animal may seem quieter, less interested in food, or reluctant to allow feeding. This page explores the signals that can accompany mastitis, the biological processes that contribute to inflammation in mammary tissue, the ways in which the condition is investigated, and the range of approaches used to support affected animals and their offspring during the nursing period.