Hyperkeratosis is a thickening of the outer layer of the skin, which contains a tough, protective protein called keratin. This thickening is often part of the skin's normal protection against rubbing, pressure and other forms of local irritation, and causes calluses and corns on hands and feet or whitish areas inside the mouth. Other forms of hyperkeratosis can occur as part of the skin's defense against chronic (long-lasting) inflammation, infection, the radiation of sunlight or irritating chemicals. Less often, hyperkeratosis develops on skin that has not been irritated. These types of hyperkeratosis may be part of an inherited condition, may begin soon after birth and can affect skin on large areas of the body.

There are many examples of hyperkeratosis, including:

• Corns and calluses – When areas of skin are exposed to repeated friction or pressure, thick layers of dead skin cells form the hardened areas we call corns and calluses. Corns usually develop on irritated toes, and calluses form on the soles of the feet and the palms of the hands. For many people, corns and calluses are simply a cosmetic nuisance, but for others, they are a painful and troublesome medical problem.



• Warts – Warts are small bumps on the skin that are caused by human papilloma virus (HPV) infection. Plantar warts grow on the soles of the feet. HPV usually is spread by direct contact, typically by touching or shaking hands with someone who already has a wart or by coming in contact with a contaminated surface, especially by walking barefoot on a gym floor or a pool deck or by wearing someone else's shoes.



• Chronic eczema – Eczema, also called dermatitis, is an inflammation of the skin that can be triggered by allergies, irritating chemicals and other factors. Eczema causes itching, redness and tiny blisters. When the inflammation is difficult to control, chronic eczema can lead to hyperkeratosis, dry skin, scaling, changes in skin color and localized hair loss.



• Lichen planus – This condition may appear as a lacy white patch on the inside of the mouth or as an itchy, violet, scaly patch elsewhere on the skin. Although the cause of lichen planus is unknown, researchers suspect that it may be related to an abnormal reaction of the immune system.



• Actinic keratoses – These are flat, red, rough sandpaperlike spots or patches of skin are caused by excessive exposure to the ultraviolet radiation of sunlight. They can be as tiny as a few millimeters. They occur on sun-exposed areas of skin, and they have the potential to develop into squamous cell carcinoma.



• Seborrheic keratoses – These are small, noncancerous skin growths. They can be tan, brown or black and are found on the face, trunk, arms or legs. Seborrheic hyperkeratoses are very common, and most people develop between 1 and 20 during their lifetime. Their cause is a mystery.



• Inherited conditions – Several inherited conditions cause hyperkeratosis. Lamellar ichthyosis, X-linked ichthyosis and ichthyosis vulgaris cause a widespread, thick, platelike scaling of the skin. Symptoms begin either shortly after birth or during early childhood.

Many forms of hyperkeratosis are painless. However, corns, calluses and plantar warts can cause a great deal of discomfort.

Depending on your specific pattern of skin symptoms, your doctor will ask whether you have a family history of skin problems, and whether you have a personal history of allergies, frequent sun exposure, use of dentures or orthodontic dental appliances, unconscious chewing on your cheek or tongue or use of smokeless tobacco.

Sometimes, your doctor can diagnose the cause of your hyperkeratosis by reviewing your history and symptoms and by examining your skin. This often is the case with corns, calluses, warts and chronic eczema. If you have chronic eczema that could be allergy-related, the doctor may suggest that you have allergy testing.

In some cases, a biopsy may be taken to confirm the diagnosis. In a biopsy, a small piece of tissue is removed to be examined in a laboratory. If your doctor suspects that you have actinic keratoses, you may need to have a skin biopsy to confirm the diagnosis and rule out skin cancer.

If your child develops hyperkeratosis in many areas of his or her body, your doctor may review your family history and skin symptoms to determine if your child has an inherited disorder.

How long a particular form of hyperkeratosis lasts depends on its cause. For example, corns and calluses usually will last as long as a person continues to wear poorly fitting shoes. Warts may disappear on their own, although this may take several months.

Once they develop, actinic keratoses or seborrheic keratoses are long-term conditions that do not disappear without treatment. Inherited forms of hyperkeratosis are lifelong conditions.

Some forms of hyperkeratosis are very easy to prevent:

• Corns and calluses – Wear comfortable shoes.



• Plantar warts – Avoid going barefoot in gyms, locker rooms or pool areas.



• Chronic eczema – Avoid potential triggers, such as extreme temperatures, dry air, harsh soaps, bubble baths or irritating chemicals to help to limit or prevent eczema symptoms. You also can try using blankets and wearing clothing made of cotton, rather than more irritating fabrics such as wool, silk and rough synthetics. Avoiding or removing triggers for your allergies also may help. When you have mild eczema, make sure you get and follow treatment advice to avoid developing chronic (long-lasting) eczema.



• Actinic keratoses – Limit your sun exposure to early morning or late afternoon hours. Wear protective clothing and a hat when you go outdoors, and always apply a sunscreen with a sun protection factor (SPF) greater than 15.

The treatment of hyperkeratosis depends on the type and possible cause:

• Corns and calluses – Using moleskin or padding next to the affected area can help to relieve pain. Avoid further irritation that stimulates growth of the corn or callus. Never try to shave away or cut a corn or callus by yourself. Consult with your health care professional or a podiatrist.



• Warts – Your health care professional or dermatologist can remove warts by freezing them with liquid nitrogen (cryosurgery), vaporizing them with a laser or trimming them away surgically. If the treatment does not reach the layer of skin infected with the virus, the wart can come back in the same place. Repeat treatments may be necessary. Although warts can be treated at home with nonprescription remedies, self-treatment may take longer than treatments in a medical setting. Self-treatment may be more effective after you have been treated by a health care professional, especially if a wart appears to be large or deep. If you have diabetes or poor circulation, you should always be treated by a health care professional to avoid injury and infection.



• Chronic eczema – Your doctor usually will treat eczema by prescribing a corticosteroid ointment or cream for you to rub into the affected area. Moisturizing the skin is also very important.



• Lichen planus – Like chronic eczema, lichen planus usually is treated with corticosteroid ointment or creams.



• Actinic keratoses – Your doctor may use cryosurgery to remove a single actinic keratosis. Multiple keratoses can be treated with skin peels, laser therapy or dermabrasion.



• Seborrheic keratoses – A seborrheic keratosis can be removed with cryosurgery or with a scalpel.



• Inherited conditions – There is no cure for these conditions. To treat large areas of scaly skin, your doctor may suggest bathing with bath oil or rubbing special emollients into the skin.

Make an appointment to see a health care professional or podiatrist if you have painful corns or calluses or if you develop a painful thickening on your foot that looks like a plantar wart. People with diabetes should have their feet examined regularly by a podiatrist to avoid skin infections from corns, calluses or warts.

All adults should examine their skin regularly after age 20, especially if they have a history of working or playing for long hours in the sun. If you are not sure how to examine your skin yourself, ask your doctor for information about the proper technique. If you think you have an area of hyperkeratosis or eczema, schedule an appointment to see a health care professional. Whenever you notice that a skin growth or mole has changed color, size or shape, you should call your doctor for a more urgent appointment. Any new mole or other growth on the skin, should be checked for signs of cancer. If you have actinic keratoses, you should also call your doctor for treatment.

Most forms of hyperkeratosis are local skin problems that have a good prognosis. Actinic keratoses can develop into squamous cell skin cancer.

American Academy of Dermatology
P.O. Box 4014
Schaumburg, IL 60168-4014
Phone: 847-330-0230
Toll-Free: 1-888-462-3376
Fax: 847-330-0050
http://www.aad.org/

American Podiatric Medical Association (APMA)
9312 Old Georgetown Road
Bethesda, MD 20814
Phone: 301-571-9200
Toll-Free: 1-800-275-2762
Fax: 301-530-2752
Email: askapma@apma.org
http://www.apma.org/

National Cancer Institute (NCI)
U.S. National Institutes of Health
Public Inquiries Office
Building 31, Room 10A03
31 Center Drive, MSC 8322
Bethesda, MD 20892-2580
Phone: 301-435-3848
Toll-Free: 1-800-422-6237
TTY: 1-800-332-8615
Email: cancergovstaff@mail.nih.gov
http://www.nci.nih.gov/