Solar Keratosis

What are solar keratosis?

These appear as scaly rough patches of skin that may itch and irritate. They are most frequently found on areas of skin that experience high levels of sun exposure. This includes the forehead, nose, cheeks,  upper lip, temples and back of the hands. Fair-skinned persons are most at risk and especially those that have lived abroad or worked outdoors. The surrounding skin may show other signs of sun-damage including brown sun-spots (solar lentigines), wrinkles (rhytides), and skin-thinning. Many people develop multiple solar keratosis on the face or scalp. Approximately 15-20% of the population aged over 65 years are expected to develop solar keratosis in the next few years.

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Why are the important?

Solar keratosis affect people by making the skin itch and scale .There is also a small risk of skin cancer (1 in 200 lesions may develop into a skin cancer called squamous cell carcinoma).

What causes solar keratosis to develop?

Ultraviolet light damages the bottom layer of skin cells called the basal layer. This layer of skin is responsible for growth of the surface skin cells and damage to the cell structure in the basal layer makes these skin cells grow abnormally. This results in excessive growth of the cells producing the rough scaly skin and damage to the cell structure (DNA) increases the risk of skin cancer. Treatments generally destroy any abnormal cells that are present in the basal layer of the skin.

Is treatment necessary?

Up to 25% of solar keratosis may resolve without any action and treatment is only necessary if they cause symptoms or cosmetic embarrassment. The daily application of a moisturiser may help to reduce the symptoms of itch, irritation and roughness of the skin.

Treatment of solar keratoses

• Solaraze Gel
  Solaraze is a gel that contains a substance called diclofenac. Diclofenac is a non-steroidal anti-inflammatory drug that inhibits the release of prostaglandins in the skin that are thought to play an important role in the development of solar keratosis. It is combined with hyaluronic acid, which aids penetration of the active ingredient into the skin. Application of the gel can help to clear early actinic keratosis. It is generally applied twice daily for 6-8 weeks. It may cause redness and irritation of the skin before clearing occurs.  

• 5-Fluorouracil Cream
  This cream interferes with the growth of abnormal skin cells that cause solar keratosis. The treated skin usually becomes red and sore before it heals. It is generally applied once or twice daily for several weeks. Intense inflammation of the skin may develop but the eventual cosmetic result is usually good. 

• Imiquinod Cream
  This is a new cream that was originally developed to treat warts by stimulating the immune system. It has shown promise for treating sun-damaged skin and superficial types of skin cancer such as basal cell carcinoma. It is applied once daily for 6-16 weeks. It causes an inflammatory reaction in the skin that may cause redness and irritation.

• Cryotherapy (Freezing)
  The abnormal skin cells that cause solar keratosis may be destroyed by freezing with cold substances such as liquid nitrogen (-196 degrees). This treatment is frequently used by dermatologists and is a very effective method for treating all types of actinic keratosis. Treatment normally causes redness and shedding of the skin surface. Treated lesions on the face may take 2-3 weeks to recover and on the lower leg it may take as a long as 12 weeks before a full recovery takes place. Light freezing usually causes no permanent damage to the skin, however, cryotherapy may cause loss in skin colour (hypopigmentation), darkening (hyperpigmentation), and rarely scarring.

• Curettage & Cautery
  It may be necessary to scrape off solar keratosis form the skin surface by curettage. This usually causes bleeding of the skin and cautery is used to stop this using an electrical device such as a hyfrecator. A scab may form that takes a few weeks to heal. A pale hypopigmented scar may develop.

• Surgical Excision
  Occasionally, solar keratoses may need to be removed by surgery under local anaesthesia. This can be used for persistent lesions and may be necessary to exclude a skin cancer. This usually involves stitches in the skin and will leave a scar associated with the surgical wound.

• Photodynamic Therapy
  Photodynamic therapy (PDT) involves applying a chemical to the skin called a porphyrin. This is absorbed by the abnormal skin cells that are responsible for producing the actinic keratosis. A red light source is then shone on the skin surface several hours later. The interaction of the chemical and the red light destroys the abnormal cells. The cosmetic result is usually very good and the treatment is being used in other types of sun-damaged skin including early Basal Cell Carcinoma and Bowen's Disease. Healing typically takes 7-9 days and the cosmetic results are excellent.

What can I do to help my skin problem?

Studies of individuals in Australia have shown that avoidance of further sun-exposure and regular application of sun-screens can help reduce the number of new solar keratosis developing. It is therefore important to protect your skin from the sun by wearing a wide-brimmed hat and using sunscreens with a Sun Protection Factor (SPF) of greater than 20, ideally 25-30. Daily application of a moisturiser to the skin may help and many daily moisturisers now contain sunscreens.