Lichen planus Dr Rob Hicks Lichen planus (LP) is an itchy rash that can appear anywhere on the body and is often mistaken for other skin complaints.

In this article

What is Lichen planus? Symptoms

Causes and risk factors Treatment and recovery

About one in 50 people may develop the condition, which most commonly affects those between the ages of 30 and 60, and women slightly more often than men. It's rare for children or older people to be troubled by lichen planus, though not impossible.

The onset of the rash is usually gradual, often first appearing on the flexor surface of the limbs (i.e. the wrists or back of knees).

After a few days the rash becomes more widespread, and it may continue to spread for several weeks. LP may also affect the genitalia and the mucous membranes (including the mouth, larynx, tonsils, conjunctivae of the eye, the bladder, vulva and vagina, throughout the gastrointestinal tract and around the anus.)

The spots of lichen planus are flat topped and pink-purple in colour, and usually measure between 3mm and 5mm. Their surface is shiny and reflects light. They may appear in groups or along the line of an injury where the skin has been knocked or scratched.

Affected skin may become raised or hypertrophic, or thin (atrophic). Hypertrophic lesions are particularly itchy.

When looked at closely, irregular white streaks can be seen. These help to identify the spots as lichen planus and are called Wickham's striae. The spots of lichen planus can be found in the skin creases of the wrists, elbows and ankles, and in the lower back and genital areas.

The Wickham's striae often appear in the mouth too, on the cheeks and the gums where the white milky streaks are more easily seen and create a lacy, net-like appearance. Mouth ulcers develop, causing soreness that's made worse by hot or spicy food.

Lichen planus can affect the scalp where it destroys the hair follicles causing patches of hair loss. Nails may be affected and become thin and damaged, forming a lengthways groove along the nail.

Although the precise cause isn't known, LP is known to be a response by the cells of the immune system to some sort of trigger, possibly a viral infection or a drug. White blood cells called lymphocytes accumulate in areas of the skin affected by the rash.

LP is often found in combination with other diseases where there is altered immunity, such as vitiligo, dermatomyositis, and ulcerative colitis. There is also a link between LP and some liver conditions such as hepatitis C and chronic active hepatitis The onset or worsening of LP has been linked to stressful events, although this link isn’t clear.

As it isn't infectious it isn't possible to pass the rash on to other people.

As it isn't infectious it isn't possible to pass the rash on to other people. LP is often mistaken for psoriasis because they can look similar. In some cases there is a family history of the condition which suggests that there may be a genetic disposition towards an immune system reaction.

When just the skin is affected, the disease usually settles on its own after a while – in more than 50 per cent of cases the rash is gone within six months (85 per cent of cases subside within 18 months). But oral LP persists much longer – on average for about five years. As it clears the spots become flatter and darker leaving the affected skin areas a slightly different colour to the normal skin, usually slightly brown or grey. The change in skin colour tends to be more pronounced for those with dark skin.

If the spots aren't itchy then no treatment is necessary. When they're causing irritating itching then this can be relieved by using calamine lotion, or emollient creams.

Oatmeal is a very good natural therapy that relieves itchy skin and oatmeal-based creams are available from your pharmacist. Steroid creams are also safely used to bring inflammation and itchy discomfort under control.

When extensive parts of the body are affected then stronger treatments are necessary and these are usually supervised by a hospital specialist. This may be tablets to turn down the immune system or ultraviolet light therapy.

If the mouth's severely affected then specialist advice and monitoring is important as the ulcers can become cancerous, although this is rare, occurring in less than 2 per cent of cases. Genital LP in women may also slightly increase the risk of cancer.

Fortunately, for most people, once cleared, lichen planus doesn't recur.

This article was last medically reviewed by Dr Trisha Macnair in March 2009.