Solar Keratosis

What is a solar keratosis?

A solar keratosis is a small, rough, bump which develops on the skin. It is caused by a lot of exposure to the sun over many years. One or more may develop. It is sometimes called an actinic keratosis.

What does a solar keratosis look like?

Each one can range from the size of a pinhead to 2-3 cm across. Their colour can be light, dark, pink, red, the same colour as your skin, or a combination of these. The top of each one may have a yellow-white crust. They feel rough and dry, and are slightly raised from the surface of the skin. You can often feel them more easily than see them. Some redness may develop in the surrounding skin.

Sometimes a finger-like growth of hard skin appears to come out of a solar keratosis (a 'cutaneous horn').

Several solar keratoses may develop at about the same time, often in the same area of skin. Sometimes several join together and form a large flat-ish rough area of skin.

Solar keratoses usually develop on areas of skin which have been exposed to the sun a lot. For example, on the face, neck, bald patches on the scalp, and the backs of the hands. They may appear in other areas in people who do a lot of sunbathing.

There are usually no other symptoms. Rarely, you may get an itchy or pricking sensation from affected areas of skin.

Who gets solar keratoses?

Solar keratoses are caused by damage to the skin by ultraviolet light which is part of sunlight. The skin is normally pretty good at repairing any minor damage. But, over the years some areas of skin are unable to cope with the repeated exposure to sun and form into a solar keratosis. So, it is not a recent bout of sun-tanning that causes them but repeated minor sun-damage to the skin over time.

People with fair skin who do not tan easily are most commonly affected. Because their skin has less protective pigment, they are the most susceptible to sunburn and other forms of sun damage. As it usually takes years of sun exposure to develop a solar keratosis, older people tend to be the most commonly affected. But, they may appear at a much earlier age in people who work outdoors, or who do a lot of sunbathing.

Are solar keratoses dangerous?

In themselves, solar keratoses are not cancerous and do no harm. They can be unsightly.

But, usually after several years, up to 1 in 10 are thought to turn into a form of skin cancer called squamous cell carcinoma. This is not the most serious form of skin cancer. It is a fairly slow growing cancer, and can usually be easily cured if treated early enough.

What is the treatment for solar keratoses?

Up to half of solar keratoses will clear away without any treatment within 1-2 years. If you only develop one, many doctors in the UK would advise that you just leave it alone (provided it is not causing any symptoms). It may go away, but see a doctor if you notice any change in the appearance or if it becomes tender. Treatment is usually advised if you have more than one solar keratosis. They can usually be easily treated.

Freezing a solar keratosis with liquid nitrogen is the common treatment. Liquid nitrogen is so cold that it destroys tissue. A solar keratosis can be easily sprayed with liquid nitrogen. It is destroyed and then falls off a few days later. A small scab is left and gradually replaced by fresh healthy skin. Liquid nitrogen often causes the surrounding skin to blister for a few days.

Cutting out or scrapping off the solar keratosis are other options. These are usually done after numbing the skin with some local anaesthetic.

A cream or gel is sometimes used, especially if you have a lot of small solar keratoses where you would otherwise need repeated freezing or minor surgery to get rid of them all.

• One type of gel contains an anti-inflammatory drug called diclofenac. This may take up to 3 months or more of treatment to clear the skin.
• Another cream which is sometimes used contains a drug called 5 fluorouracil. This kills the abnormal cells and fresh normal skin grows back. This cream works more quickly (4 weeks) but usually causes quite a lot of inflammation and blistering of the surrounding skin for a while. It is usually only prescribed by skin specialists.

Other risks if you have a solar keratosis

If you have one or more solar keratosis it is a 'marker' that you have had a lot of sun exposure. The more serious type of skin cancer, melanoma, most commonly occurs in people who have had a lot of sun exposure. So, although an solar keratosis does not progress into a melanoma, if you have an solar keratosis your risk of developing a melanoma at some other part of your skin is increased. So, tell a doctor soon if you notice any changes in any part of your skin such as new moles, small dark patches developing, etc.

Can solar keratoses be prevented?

If you spend much time in the sun you have an increased risk of developing solar keratoses, certain types of skin cancer and various other skin problems. So, to reduce the risk of developing these conditions we should all:

• Stay out of strong sunlight.
• Avoid the noonday sun (between 11 am and 3 pm).
• When out in the sun:
  • seek natural shade in the form of trees or other shelter.
  • wear clothes as a sunscreen including T-shirts, long-sleeved shirts, and hats.
  • use a broad spectrum sun screen with an sun protection factor (SPF) of 15 or higher to protect against UVB and UVA.

© EMIS and PIP 2004   Updated: April 2003   CHIQ Accredited