Hyperkeratosis is a thickening of the outer layer of the skin. This outer layer contains a tough, protective protein called keratin.
This skin thickening is often part of the skin's normal protection against rubbing, pressure and other forms of local irritation. It causes calluses and corns on hands and feet. It can cause whitish areas inside the mouth.
Other forms of hyperkeratosis can occur as part of the skin's defense against:
- Chronic (long-lasting) inflammation
- Radiation of sunlight
- Irritating chemicals
Less often, hyperkeratosis develops on skin that has not been irritated. These types of hyperkeratosis may be part of an inherited condition. They may begin soon after birth and can affect skin on large areas of the body.
There are many examples of hyperkeratosis. They include:
- Corns and calluses. Corns and calluses develop in areas of skin exposed to repeated friction or pressure. In response, thick layers of dead skin cells pile up and harden.
Corns usually develop on irritated toes. 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. It is typically spread by touching or shaking hands with someone who already has a wart. It may also be spread by coming in contact with a contaminated surface. For example, by walking barefoot on a gym floor or a pool deck or by wearing someone else's shoes.
- Chronic eczema. Eczema is an inflammation of the skin. It can be triggered by allergies, irritating chemicals and other factors. Eczema is also called dermatitis.
Eczema causes itching, redness and tiny blisters. When the inflammation is difficult to control, chronic eczema can lead to:
- Dry skin
- Changes in skin color
- Localized hair loss
- Lichen planus. This condition may appear as a lacy white patch on the inside of the mouth. Or it may be an itchy, violet, scaly patch elsewhere on the skin. Lichen planus may be related to an abnormal reaction of the immune system.
- Actinic keratoses These are flat, red, rough, sandpaper-like spots or patches of skin. They can be as tiny as a few millimeters.
They are caused by excessive exposure to the ultraviolet radiation of sunlight. They occur on sun-exposed areas of skin. And they have the potential to develop into skin cancer.
- Seborrheic keratoses These are small, noncancerous skin growths. They can be tan, brown or black. They appear on the face, trunk, arms or legs. Seborrheic hyperkeratoses are very common. Their cause is a mystery.
- Inherited conditions. Several inherited conditions cause hyperkeratosis. They 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
- Have a personal history of allergies
- Have frequent sun exposure
- Use dentures or orthodontic dental appliances
- Unconsciously chew on your cheek or tongue
- Use smokeless tobacco
Sometimes, your doctor can diagnose the cause of your hyperkeratosis based on 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 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 actinic keratoses, you may need to have a skin biopsy to confirm the diagnosis and to rule out skin cancer.
If your child develops many areas of hyperkeratosis, your doctor may review your family history and skin symptoms. This will help 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 last as long as a person continues to wear poorly fitting shoes. Warts may disappear on their own. But this may take several months.
Once they develop, actinic keratoses or seborrheic keratoses are long-term conditions. They 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 to help to limit or prevent eczema symptoms. For example, avoid:
- Extreme temperatures
- Dry air
- Harsh soaps
- Bubble baths
- Irritating chemicals
Also, try using blankets and clothing made of cotton. Fabrics such as wool, silk and rough synthetics can be more irritating. Avoiding or removing triggers for your allergies also may help.
Get advice and treatment for mild eczema to help prevent it from becoming a long-lasting condition (chronic eczema).
- Actinic keratoses. Limit your sun exposure to early morning or late afternoon hours. Wear protective clothing and a hat when you go outdoors. Apply sunscreen to exposed areas with a sun protection factor (SPF) of a least 30.
The treatment of hyperkeratosis depends on the type and possible cause.
- Corns and calluses. Use moleskin or padding next to the affected area to decrease pain. Always wear proper footwear to avoid further friction.
Don't shave away or cut a corn or callus on your own. Consult a health professional for advice and treatment.
- Warts. A health care professional can remove warts. This is done by one of the following:
- Freezing them with liquid nitrogen (cryosurgery)
- Vaporizing them with a laser
- 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.
Warts can be treated at home with nonprescription remedies. Self-treatment will take longer for the wart to go away compared to treatment in a medical setting. Self-treatment may be more effective after you have been treated by a health care professional. This is especially true 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. This will help you to avoid injury and infection.
- Chronic eczema. Your doctor usually will prescribe a corticosteroid ointment or cream. 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. This 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 rubbing special emollients into the skin.
Make an appointment to see a health care professional or podiatrist if:
- You have painful corns or calluses
- 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 health professional to avoid skin infections from corns, calluses or warts.
Adults should examine their skin regularly after age 20. This is particularly true for those who have a history of working or playing for long hours in the sun. If you are not sure how to examine your skin, ask your doctor for guidance.
If you think you have hyperkeratosis or eczema, schedule an appointment with a health care professional.
Whenever you notice that a skin growth or mole has changed color, size or shape, call your doctor for a more urgent appointment. Any new mole or other growth should be checked for signs of cancer.
If you have actinic keratoses, 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
American Podiatric Medical Association (APMA)
9312 Old Georgetown Road
Bethesda, MD 20814
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