Seborrhoeic keratoses are one of the most common spots or lumps on the skin. Because they often develop on previously normal skin and appear different from other spots on the body, they frequently cause concern. Fortunately, they are harmless and treatment is rarely required.
What are seborrhoeic keratoses?
Seborrhoeic keratoses — also known as seb k, stucco keratoses, senile keratoses, senile warts and “barnacles” — are a common and harmless condition affecting the top layer of skin.
How common are seborrhoeic keratoses?
Almost every Australian over 50 has at least one seborrhoeic keratosis. With increasing age, more seborrhoeic keratoses appear. It’s common for people over 75 to have dozens. Although seborrhoeic keratoses are especially common in older people, about a quarter of young adults (aged 15-30) have them.
Seborrhoeic keratoses can appear on most parts of the skin (but rarely on the palms, soles or genitals). They are more likely to appear on areas that have been exposed to sunlight, but they don’t always appear on these areas.
Seborrhoeic keratoses tend to be more common in people whose parents or grandparents have many.
There is no known way of preventing them from appearing.
The appearance of seborrhoeic keratoses varies widely.
A typical seborrhoeic keratosis is slightly raised and has a “stuck-on” appearance. The edges are usually clearly defined, and it’s possible to pick at them. They may be very dry, rough and crusty, or smooth and waxy in consistency.
The colour is usually darker than the surrounding skin, but can be black, dark brown, grey, yellow, white, or skin-coloured.
Usually a doctor can diagnose a seborrhoeic keratosis by looking at it and feeling its consistency. High magnification examination with a dermoscope usually shows characteristic features.
Sometimes seborrhoeic keratoses don’t exactly fit these criteria, and even an experienced doctor might find them challenging to identify.
In some cases, they can look like skin cancers (melanoma or squamous cell carcinoma) — and a small number of melanomas look like seborrhoeic keratoses and can potentially be missed.
If there is any doubt about the diagnosis, the spot should be biopsied. This is commonly done by shaving it off the surface of the skin. The specimen can then be examined by a skin pathologist to provide a diagnosis.
If you have a single or small number of suspect spots, they can be examined by our doctor during a mole check appointment.
Seborrhoeic keratoses have no dangerous complications, but people often don’t like them because:
- occasionally they are very itchy
- they may be unsightly
- they may become irritated or caught in clothing
Some people think of them as a reminder of ageing, even though they are also common in young people.
The main medical concern is that in people with many seborrhoeic keratoses, it could be difficult to identify a new or changing melanoma or other skin cancer in a region surrounded by many other dark or raised spots.
Because seborrhoeic keratoses are harmless, it’s not medically necessary to treat them. They are usually treated for cosmetic reasons or because they are itchy or irritated.
Unfortunately, seborrhoeic keratoses frequently return after treatment.
After soaking the seborrhoeic keratosis (in a bath or swimming), gently rub it with a rough object such as an exfoliating glove, pumice stone, emery board or even fine sandpaper. This treatment may need to be repeated several times, but tends to give a good cosmetic result.
Salicylic or lactic acid
Salicylic and lactic acid preparations dissolve rough, dry and crusted skin, and can be helpful in breaking down seborrhoeic keratoses. They are available over the counter as Calmurid or Coco-Scalp. Stronger concentrations of salicylic acid are more effective but need to be prescribed by a doctor.
A doctor can freeze off seborrhoeic keratoses on the spot during a consultation. This treatment is popular because it usually only needs to be performed once. Disadvantages of this treatment include pain, blistering and redness at the treated site, and a small risk of scarring.
There is no Medicare rebate for this treatment, so there may be an out of pocket expense.
Shave or excision
If the diagnosis of a seborrhoeic keratosis is not obvious, a doctor can shave it off the surface of the skin or cut around it to remove it. This is best way to confirm the diagnosis and rule out skin cancer in uncertain cases.
Concentrated hydrogen peroxide is an effective treatment for seborrhoeic keratoses. It is a powerful bleach and must therefore be used with extreme caution.