Ask the SkinVet

I adopted my dog Rufus from an animal shelter 3 weeks ago. He was fine when I brought him home, but he is now very itchy and has scabs on his skin. What could it be? —Eric J., Portland, OR
Frequently Asked Questions

Dear Eric,

It is unfortunate, but many wonderful animals are surrendered to animal shelters, humane societies, and rescue organizations because they have skin issues and diseases that are not well controlled. Thank you for giving Rufus another chance at life! It is possible that his itchiness (pruritus) was masked by medication when you adopted him, that he has a seasonal skin disease like atopic dermatitis, or that he was exposed to a contagious skin disease either before or during his stay at the shelter. You need to see a veterinarian or veterinary dermatologist to diagnose the problem. The best case scenario is that he picked up something contagious while stray or in the shelter. If that is the case, his condition could be curable, whereas many other skin diseases need to be managed long term. A few of the more common contagious skin diseases that he might have been exposed to are sarcoptic mange (scabies) and ringworm (dermatophytosis).

Sarcoptic mange (scabies) is diagnosed by your veterinarian or veterinary dermatologist based on the clinical signs (it usually causes intense itching, red bumps (papules) and scabs (crusts) on the ear margins, elbows, and underside) and based on the results of a test called a skin scraping. A skin scraping collects a small amount of material from the outer layer of skin (epidermis) for examination under the microscope. Mites are relatively hard to find with sarcoptic mange, so your veterinarian may recommend treatment regardless of whether or not they find mites. Treatment may consist of selamectin (Revolution®), lime sulfur dips, ivermectin, fipronil (Frontline® Spray), or milbemycin (Interceptor®). My first choice is Revolution®, but follow your veterinarian’s or veterinary dermatologist’s advice. Some of these products have specific contraindications for particular animals.

Ringworm (dermatophytosis) is a fungal infection of the skin and hair. Athlete’s foot is an example of ringworm in people. Like sarcoptic mange (scabies), ringworm (dermatophytosis) is a contagious disease that Rufus could have picked up when potentially exposed to other dogs. Cats tend to be the carriers of the most common cause, Microsporum canis. One species of ringworm in particular, Trichophyton mentagrophytes, can cause intense itching (pruritus) in dogs. Again, your veterinarian or veterinary dermatologist would need to test for ringworm (dermatophytosis) with a fungal culture. A quick, but inaccurate test is the Wood’s light. Certain species of ringworm will cause the hair to glow an apple-green color when illuminated with a Wood’s light. A direct examination of the hair (trichogram, KOH preparation) under the microscope may provide a quicker diagnosis with experience; however, not all veterinarians perform this test regularly. The treatment of ringworm involves the use of shampoos, dips, rinses, creams, and/or oral antifungal medications (often ketoconazole, fluconazole, itraconazole, griseofulvin, or terbinafine) under the close supervision of your veterinarian or veterinary dermatologist.

I hope you find this information helpful. Your veterinarian’s or veterinary dermatologist’s (find one at www.acvd.org) examination will help narrow down the possibilities.

Wishing comfortable skin for Rufus,
The SkinVet, Jon D. Plant, DVM, DACVD
Board-certified veterinary dermatologist
SkinVet® Clinic, PLLC Lake Oswego, OR

Dr. Plant's answers in "Ask the SkinVet" are made without the benefit of a physical examination. Treatment should not be based on these answers only after an examination by a qualified veterinary professional. For more information, see the web site of the American College of Veterinary Dermatology.