Actinic keratoses, also known as solar keratoses, are dry scaly patches of skin caused by damage from years of sun exposure. The patches are usually harmless but can be itchy and look ugly.
They are pink, red or brown in colour and range in width from 0.5 to 3cm. Actinic keratoses only tend to be seen in people over the age of 40.
Sometimes the skin can become very thick over them and occasionally they can look like horns or spikes.
Where are they found?
Actinic keratoses are found on areas of skin that are exposed to the sun. They are most commonly found on the:
- face, especially the nose and forehead
- forearms and backs of hands
- (in men) on the rims of the ears and bald scalps
- (in women) on the legs below the knees
Who is affected?
Actinic keratoses are most commonly seen in fair-skinned people, especially those with blue eyes, red hair, freckles and a tendency to burn in the sun. Men are more affected than women.
People who have lived or worked abroad in a sunny place or who have worked outdoors or enjoy outdoor hobbies are most at risk.
It may take many years before actinic keratoses develop – they don't usually appear before the age of 40.
How are they diagnosed?
Your doctor may be able to diagnose actinic keratoses just by their appearance. The diagnosis may need to be confirmed by taking a skin sample and examining it under the microscope.
If the patches are not troublesome, your doctor may simply recommend that you keep an eye on them and come back if they change in any way or become troublesome.
Actinic keratoses are usually removed because of concerns they may turn into skin cancer (see below) or, less commonly, for cosmetic reasons.
The symptoms can be improved using a variety of treatments, which are summarised below.
Cream or gel
Efudix cream (5-fluorouracil, Aldara cream ([imiquimod]) or Solaraze gel ([diclofenac sodium]) are commonly used when there are many patches, for example on the scalp.
The cream or gel is applied daily (using gloves) for several weeks and causes the abnormal skin cells to die. It can make the skin sore and it may weep and blister after a few days of treatment.
There are pros and cons to the preparations:
- Aldara and Efudix cream are more effective, and you'll only need to use them for four weeks. However, they cause more of the above mentioned skin effects and you should avoid the sun while you are using them.
- Solaraze gel has generally fewer adverse skin effects but doctors feel it is less effective, so you will have more patches at any one time and treatment lasts longer (12 weeks).
Photodynamic therapy can also be effective in treating actinic keratoses, but this is painful and not widely available. It involves applying a cream containing a drug that is activated when blue light is shined onto it. The drug in the cream reacts with oxygen to form a chemical that kills the cancer cells.
Freezing with liquid nitrogen
Also known as cryotherapy, freezing causes blistering and shedding of the sun-damaged skin. The time it takes to heal varies depending on where on the body it is found:
- keratoses on the face peel off after about 10 days
- those on the hands go away after about three weeks
- those on the legs can take about 12 weeks to heal
A light freeze usually leaves no scar but longer freezes (used for thicker lesions or early skin cancer) may leave a pale or dark mark.
This is done under a local anaesthetic and is generally used for thicker patches and early skin cancers, or for diagnosis.
Cautery (heat treatment) is then used to stop any bleeding. A scab forms, which heals over a few weeks to leave a small scar. The scrapings are looked at under the microscope to confirm the diagnosis.
Cutting it out (excision biopsy)
If your doctor suspects the patch may be cancerous or pre-cancerous, they may cut it out using a scalpel under local anaesthetic and close the wound with stitches. The piece of skin is then looked at under the microscope to confirm the diagnosis.
Removing the patch leaves a permanent scar.
When you might need to see a specialist
Actinic keratoses can often be managed by your doctor. You may need to see a specialist if:
- your doctor thinks the patch may be cancerous or pre-cancerous
- the patch is larger than 1cm
- the patch has not responded to treatment
- you are taking immunosuppressant drugs (following a transplant, for example)
Skin cancer risk
Rarely, actinic keratoses can develop into a type of skin cancer called squamous cell carcinoma, which will need removing under local anaesthetic.
You or your doctor would recognise this because the patch would begin to grow quickly, bleed or form an ulcer.
It is important to protect your skin from the sun if you have actinic keratoses. Use sunscreen with a sun protection factor (SPF) of at least 30, and wear a hat daily during the summer months.
Read more about staying safe in the sun.
Actinic keratoses that have been treated will usually go away, but it is very likely that more patches will develop, requiring further treatment.
The development of actinic keratoses is a sign that the underlying skin is damaged from many years of sun exposure, and this cannot be reversed. It means you have a higher than average risk of developing skin cancer.