Hyperkeratosis is the thickening of the outer layer of skin, resulting in a variety of conditions, including eczema, psoriasis, corns, warts, and calluses. It occurs when the keratin (a protein that makes up the outer layer of skin) starts to overgrow. 

Some forms of hyperkeratosis are inherited conditions, while others develop later in life. In some cases, it may be the response of the skin to friction and rubbing. On occasion, hyperkeratosis may be an early sign of skin cancer. 

Treatment of hyperkeratosis usually involves medication to alleviate the symptoms, or removal of growths by a physician. Drug classes commonly used to treat hyperkeratosis include humectants, keratolytic agents, and plain topical corticosteroids.