Reviewed and fact checked by Bruce Whittle, DVM
Skin conditions are common in dogs. While many conditions are relatively straightforward and easy to diagnose, they can also be very complicated, especially when they arise as a result of a complication from systemic disease. Allergic skin conditions are very common and can result from many different causes including flea allergies, food allergies and environmental allergies. Skin conditions can also be caused by bacteria, fungi or parasites. Skin conditions may present as alopecia (hair loss), scaling or crusting, redness, masses in or on the skin or constant scratching, licking or biting at an area.
Flea Allergy Dermatitis
Hair loss due to scratching from flea allergy dermatitis is probably the most commonly observed skin condition in dogs. When fleas bite a dog they leave a small amount of saliva behind, which many dogs are allergic to. This sets off a cycle of itching and scratching. Thankfully we live in an era where there are many options for flea control including topical spot-ons, oral products, shampoos, and sprays that help reduce this exposure. Fleas can be difficult to see but careful examination of the base of the hair over the rump can show little black specks that look like pepper. This is digested blood and is actually flea “poop”. Controlling then preventing flea infestation will solve this problem.
Food Allergies
Some food ingredients, often protein sources, can cause an abnormal immune response in specific dogs. Food allergies in dogs commonly present as redness of the skin, itching, hair loss, and ear infections. Because of the wide array of potential offending food ingredients, diagnosis can be a challenge. Elimination diets that exclude certain potential allergens and often have a limited number of ingredients are fed for a period of time to determine if the condition improves. Different diets are tried until success is achieved. Unfortunately, this is a trial-and-error process as specific allergy testing is not effective with food allergy problems. Fortunately, persistence can usually find a diet that an affected dog will tolerate that will not stimulate allergy problems.
Environmental Skin Allergies
Another form of allergy affecting the skin is encompassed under the umbrella term of environmental skin allergies and causes a condition called atopic dermatitis. This category can include allergies to things such as house dust mites, various plant pollens and molds. Some of these potential allergens such as pollens are seasonal in nature but others such as dust mites and mold are available to cause problems throughout the year. Diagnosis may require intradermal skin testing that consists of injecting various allergens to determine which ones a dog reacts to. Specific treatment may consist of hyposensitization where tiny doses of the identified problem allergens are periodically injected until the dog no longer reacts to them. Because environmental allergens can be difficult to avoid other treatments may include anti-inflammatory or immunomodulatory medications that blunt the allergic response, bathing with medicated shampoos and nutritional supplementation with Omega-3 fatty acids. Though environmental allergy problems can rarely be cured, there are a lot of treatment options available that will improve your dog’s comfort.
Pyotraumatic Dermatitis ( “Hot Spot”)
Another very common skin condition diagnosed in dogs is known as pyotraumatic dermatitis or more commonly a “hot spot”. These lesions are usually in a small area and result from trauma due to scratching or excessive moisture that allow bacteria or fungi to invade and infect the skin. Dogs with longer, thicker hair seem to be more commonly affected than dogs with short hair. Hot spots can be a manifestation of other skin diseases so treatment of the underlying cause can be important. Treatment consists of cleaning the area and preventing further self-induced trauma by using topical anti-inflammatories and, in more severe cases, collars or cones that do not allow the dog to lick or bite at the affected area.
Parasitic (Mange) Mites
Other parasites that can also cause skin issues in dogs are Demodex or Sarcoptic mites. These mites cause skin lesions commonly referred to as mange. Demodex mites can be found in many dogs but don’t usually cause problems unless there is an underlying immune suppression that allows the mites to proliferate. Demodectic mange is not considered to be contagious to other dogs. On the other hand, Sarcoptic mites are contagious to other dogs. Additionally, they are zoonotic which means they can also be spread between animals and people. Diagnosis of skin mites is made by scraping the skin deeply with a scalpel blade then examining the scraped-up debris under a microscope. In the past, treatment required bathing or dips with insecticides but now there are oral medications that are effective and have a wider safety margin.
Alopecia
Another fairly common skin condition is called alopecia which means hair loss. Alopecia is more of a clinical sign than a specific condition. While there are numerous causes for alopecia, many of them are related to metabolic issues such hypothyroidism or hypoadrenocorticism. Diagnosis often includes blood testing to diagnose these metabolic diseases, culture to diagnose fungal infections such as ringworm, or skin scraping to diagnose parasites including mites. Specific treatment depends upon the specific diagnosis. Metabolic causes of alopecia may require life-long treatment while parasitic or fungal causes can generally be cured.
Skin Tumors
There are many types of skin neoplasia (cancer) that can affect dogs. Mast cell tumors are the most common malignant tumor in dogs and can be very locally aggressive. Lipomas are benign skin tumors that do not spread but can become large enough that they can interfere with walking depending upon location. Though these are the most common skin tumor types, there are many other possible skin neoplasia in dogs. Diagnosis is often achieved through cytology which involves using a needle and syringe to aspirate cells from the mass. The collected sample is then examined under a microscope. A surgical biopsy is another option. The sample is sent to a lab to be thin-sliced for examination under a microscope. Obtaining a diagnosis is important because it guides a surgeon as to how much tissue should be removed around the tumor to try to make sure the whole tumor is removed and the chance of recurrence is low. In some aggressive neoplasia such as mast cell tumors, therapies such as radiation or chemotherapy are combined with surgical removal. The prognosis for skin tumors is best when treatment is initiated early in the process.
Summary
Skin conditions are very common in dogs. There can be many different causes but many of them can appear the same making diagnosis more difficult. Obtaining an accurate diagnosis is important to determine the appropriate treatment. Some conditions can be cured while others such as environmental allergies or metabolic conditions may require life-long management. Early diagnosis and treatment will help your dog avoid the discomfort that accompanies many skin conditions.
