Lichen planus

An itchy purple rash and white lacy patches in the mouth. The mouth form is long-term and carries a small cancer risk needing monitoring.

What it is

An inflammatory condition thought to be autoimmune, affecting the skin, mouth, genitals, nails and scalp.

On the skin it causes intensely itchy, flat-topped, purple or darker papules, often on the wrists, forearms, ankles and lower back, sometimes with fine white lines across them. Skin lichen planus usually settles by itself within one to two years, often leaving darker marks that fade slowly.

**Oral lichen planus behaves differently: it is usually long-term**, causing white lacy patches on the inside of the cheeks, and sometimes painful red or ulcerated areas. It affects around 1 to 2 per cent of adults, more women, and it carries a small but real increased risk of mouth cancer, in the region of 1 per cent over ten years. That is why long-term dental monitoring is recommended, and why any persistent ulcer, lump or thickened white patch must be assessed rather than attributed to the condition.

Genital lichen planus can cause scarring and is frequently missed; in women it can be mistaken for lichen sclerosus or thrush for years.

Scalp involvement causes permanent scarring hair loss, so it needs treating promptly.

Nail involvement can destroy the nail permanently.

Some medicines and hepatitis C can cause a similar rash.

Signs you might notice

Skin: intensely itchy, small, flat-topped, shiny purple or darker bumps, often on wrists, ankles and lower back, sometimes with fine white lines.

New lesions appearing in a scratch or a scar.

Mouth: white lacy patches inside the cheeks; red, sore or ulcerated areas; sensitivity to spicy or acidic food.

Genital: soreness, burning, white patches, and in women, scarring and narrowing.

Scalp: redness and scaling around hair follicles, with patchy hair loss and shiny scarred skin.

Nails: thinning, ridging, splitting, or loss of the nail.

Urgent: any persistent ulcer, lump, or thickened or raised white patch in the mouth lasting more than three weeks. See head and neck cancer.

Also: rapid scalp hair loss with scarring, which needs prompt treatment to prevent permanence.

How it can affect day-to-day life

The itch of skin lichen planus is severe and is what people find hardest; strong topical steroids and antihistamines at night help.

Oral disease is managed rather than cured, and flares are triggered by stress, trauma from sharp teeth or dentures, and certain foods. A dental review to smooth sharp edges and check denture fit is genuinely therapeutic.

Sodium lauryl sulphate in most toothpastes irritates; an SLS-free toothpaste often reduces symptoms noticeably and costs the same.

Spicy, acidic and salty foods, and alcohol-containing mouthwashes, all aggravate the mouth.

Regular dental checks, usually every six to twelve months, are the monitoring that matters, and people frequently stop attending once told it is benign.

Genital involvement affects sex and is rarely asked about; scarring is preventable with treatment and not reversible afterwards.

Smoking and alcohol both raise the mouth cancer risk further and are worth addressing directly in this group.

Supporting someone well

Use the topical steroid as prescribed and for long enough; under-treatment is the usual reason it persists.

Switch to an SLS-free toothpaste and avoid alcohol-based mouthwashes.

Get sharp teeth smoothed and dentures checked; trauma perpetuates it.

Keep regular dental checks for monitoring; this is the main reason for follow-up.

Report any mouth ulcer, lump or thickened white patch lasting three weeks.

Ask about genital involvement, and treat it promptly to prevent scarring.

Get scalp involvement treated urgently; the hair loss becomes permanent.

Stop smoking and reduce alcohol.

Ask about a medication review and hepatitis C testing where relevant.

Where to get help

A GP practice or dentist for diagnosis; dermatology, oral medicine or gynaecology for specialist care.

A dentist for ongoing monitoring of oral disease.

Urgent referral for any suspicious mouth lesion.

British Association of Dermatologists and Oral Health Foundation publish patient information.