A dog may have swollen lips for several reasons, such as injury or an allergic reaction. Some causes of swollen lips can be treated at home with medication, but when the reasons for the swelling are not clear, a veterinarian can make an accurate diagnosis.
Rocky Mountain Spotted Fever
Caused by the Rickettsia ricketsii bacteria, Rocky Mountain Spotted Fever (RMSF) can be transmitted to dogs via tick bites. A high fever is usually the first sign, and occurs four to five days after the bite. Blood spots may form on the lips and gums and on areas of the skin with no hair. Swelling affects the legs, lips and ears, and the sheath covering the penis. In the later stages of the disease or during recovery, leg damage can become so severe that shedding of the skin and tissues can occur.
A single sting by a bee or wasp is usually not a serious problem, but if a dog is stung on the nose, mouth or head, it needs to be observed carefully to make sure that swollen lips do not interfere with its ability to breathe or swallow. Stings that swell significantly after just a few minutes should be seen immediately by a veterinarian. Multiple stings by a swarm of bees or wasps can create more damage, and can even be life-threatening. An owner should put as much distance as possible between the dog and the swarm by picking up the dog, running for shelter and seeking immediate medical attention.
Melanoma is a type of cancer in which melanocytes, which are the pigment-producing cells of the skin, multiply in an irregular way, eventually invading surrounding tissues. Malignant melanomas spread from the site of the original tumour, and are transported via the blood and lymph vessels to the lymph nodes and distant organs. Melanoma occurs most frequently in older dogs. A malignant melanoma on the lips of a dog will have irregular borders with a variety of different colours. A dog may have swollen lips because of the rapid growth of the melanoma lesion. Symptoms of melanoma, such as facial swelling, drooling and difficulty chewing and swallowing, are similar to those caused by dental problems, so a dog may not be diagnosed with melanoma until it is in the later stages of the disease.