If your dog's skin appears darker than usual, there's no need to panic. There are plenty of benign conditions that can cause hyperpigmentation (skin discoloration). However, some conditions may require medical attention, so it's a good idea to speak to your veterinarian any time you notice unusual changes in your pet's skin.
Primary hyperpigmentation is rare and usually only occurs in dachshunds. Symptoms of the condition, evident about the time the puppy is a year old, include a darkening and thickening of the skin from light brown to black, often in areas that have no fur. Over time, the edges of the affected areas may become red, indicating the presence of a secondary bacterial or yeast infection. There may be a loss of fur and oozing fluids as the area becomes infected. The darkening may spread throughout the body, eventually affecting the genitalia. Your dog may or may not itch, but chronic itching of the darkened skin may be caused by the secondary infection. There is no cure for primary hyperpigmentation, only symptomatic treatment and relief.
Secondary hyperpigmentation can occur in any breed of dog and is usually caused by one of several factors, including obesity, a hormonal imbalance, an allergic reaction, skin infections, parasites, bruising or dermatitis. Your veterinarian will need to examine your dog carefully to determine the underlying cause of his skin discoloration and prescribe the appropriate treatment. With proper and prompt treatment, most forms of secondary hyperpigmentation can be cured.
Your veterinarian may ask for a stool sample to rule out internal parasites. She will check for skin mites, fleas and other potential sources of irritation and may ask if your groomer has changed shampoos or if your dog is eating a new brand of food, which could indicate an allergic reaction. She may take a skin scraping or smear to check for worms or bacterial infections or the presence of yeast.
If she suspects thyroid or adrenal disease, she may order endocrine function testing, a blood work panel or a urinalysis.
A biopsy of your dog's skin can help to identify the type of bacteria present. Your vet may suggest a food trial to uncover any food allergies.
Treatment vs. Cure
Primary hyperpigmentation cannot be cured, but your veterinarian can treat your dog's discomfort with prescriptions for applied or injected steroids and medicated shampoos.
Treatment of secondary hyperpigmentation will depend upon the underlying cause of your dog's skin discoloration. Bacterial infections will be treated with oral or applied antibiotics. Antihistamines can help to relieve your dog's allergies. Medicated shampoos will help relieve itching and dry skin. If your dog has a hormonal or thyroid disorder, your vet can prescribe medications that will help to make him well. Parasites and worms can be treated with oral medications, and allergies can be managed by a change in diet.