Hyperkeratosis is a condition where excess keratin (structural protein of the skin) is produced causing the skin to thicken or harden. This can happen on the skin (especially pressure points such as elbows), paw pads, and nasal planum. If hyperkeratosis becomes more pronounced, it can lead to secondary infections and cracking of the skin. 

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Typically, a dog’s epidermal turnover time is 22 days. If this epidermal turnover rate is altered, then epidermal thickness changes abnormally. Conditions of hyperkeratosis can be split into congenital and acquired. Acquired hyperkeratosis is seen more often. A classic example of acquired hyperkeratosis is an elbow callus in a mature, large breed dog. 

Another common form is nasal hyperkeratosis which can be seen in any breed, but especially boxers, Boston terriers, and English bulldogs. This is due to abnormal facial architecture that does not allow the dorsal portion of the nasal planum to rub frictionally on common surfaces such as food dishes.

Diagnosis of hyperkeratosis may be made clinically or require a biopsy depending on the clinical presentation. Histopathology findings include epidermal hyperplasia and marked parakeratotic or orthokeratotic hyperkeratosis. Histopathology rules out other important differential diagnoses such as pemphigus foliaceus, discoid lupus erythematosus, drug reaction, etc.

The formation of abnormal keratin cannot be prevented in canine hyperkeratosis. Like many other dermatologic conditions, the disease is managed long-term. Topical treatments are typically recommended to provide hydration to the affected area. These can include ingredients such as salicylic acid, urea, petrolatum, and propylene glycol.

Salicylic acid is a keratolytic that causes desquamation of the stratum corneum without affecting the structure of the epidermis. It helps to increase the moisture of the skin while allowing keratinocytes to shed easier. Urea is also a keratolytic that moisturizes the skin by softening keratin and promoting desquamation which normalizes the epidermis. Using urea in a topical formulation allows the product to feel less greasy which is preferable to owners. A successful topical product used in cases of hyperkeratosis (especially nasal hyperkeratosis and calluses) includes 6.6% salicylic acid and 5% urea.

Petrolatum can be found easily by owners over-the-counter. It has lubricating and coating properties that can help increase water retainment to the skin. However, it is thick, greasy, and can easily stain carpet and furniture around the house if not allowed to dry after application. Propylene glycol is a lipid solvent and removes fats from the skin. It acts as a humectant and keratolytic similar to the other therapies.

Though hyperkeratosis is often viewed as a cosmetic issue, it is an abnormality that can lead to cracking of the skin, bleeding, discomfort for the pet, and secondary infections. Conditions related to hyperkeratosis can’t be cured, but can be managed to provide the pet a good quality of life. It is important for owners to understand lifelong therapy will be required.