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Lichen Planus: A Long-Lasting Inflammatory Skin Condition with Unknown Cause

What Is It?

Lichen planus (LP) is a long-term inflammatory condition affecting the skin and mucous membranes. It usually shows up as itchy, flat-topped bumps with sharp edges, often purple or reddish-purple in colour. This non-infectious condition can affect the skin, nails, scalp, mouth, and genitals. While it can appear at any age, it’s most common in adults aged 30 to 60.

Although it’s not dangerous, LP can seriously affect quality of life because of ongoing itching, involvement of mucous membranes, or scarring hair loss in more severe cases. For most people, the condition clears up on its own within months or a few years, but it can come back.

What Causes It and What Can Trigger It?

The exact cause of lichen planus remains unknown. It’s thought to be a type of autoimmune reaction where certain immune cells attack the skin’s basal cells. Some factors linked to triggering or worsening LP include:

Hepatitis C virus (HCV) infection, especially in oral and erosive forms;
Medications: Such as blood pressure drugs, antimalarials, diabetes medicines, NSAIDs, and some heart medications;
Exposure to heavy metals: Like gold, mercury, arsenic (for example, from dental fillings);
Other autoimmune diseases: LP can occur alongside conditions like vitiligo, alopecia areata, or thyroid inflammation;
Stress: Both emotional and physical stress may trigger or worsen symptoms.

Skin Lichen Planus: What to Look For

On the skin, lichen planus usually appears as:

Several flat-topped, polygon-shaped bumps about 3–5 mm across, often appearing in symmetrical groups;
Colour: Pink, red, or purple, often shiny because of their smooth surface;
Wickham striae: Fine, white, lace-like lines visible on the bumps;
Itching: Can range from mild to severe, often worse with heat or stress;
Where it appears: Commonly on wrists, forearms, lower back, ankles, and shins. Sometimes the spots join together into larger patches or line up in patterns where the skin has been injured (known as the Koebner phenomenon);
Thickened patches: These can develop on the shins or ankles in a form called hypertrophic LP.

Because it can look like eczema, psoriasis, or fungal infections, the first signs of LP are sometimes misdiagnosed. A careful skin check is important to get the right diagnosis.

When It Affects Mucous Membranes, Nails, Scalp, or Genitals

Oral Lichen Planus

Oral lichen planus (OLP) usually shows up as white, lace-like patches inside the mouth, known as Wickham striae. These are often found on the inside of the cheeks, tongue, or gums. In the erosive type, painful ulcers, redness, burning, and discomfort—especially when eating spicy or acidic foods—can occur. OLP can last for years and carries a small but important risk of turning into cancer.

Nail Lichen Planus

LP can affect one or more nails, causing:

Thinning and vertical ridges;
Splitting and brittle nails;
Pterygium: When the skin at the nail fold sticks to the nail bed, causing scarring;
Complete nail loss: In severe, untreated cases.

Scalp (Lichen Planopilaris)

When LP affects the scalp, it can cause small bumps around hair follicles, redness, and flaking. If it progresses, it may lead to scarring hair loss, which is permanent. Early treatment is key to saving hair follicles.

Genital Lichen Planus

In the genital area, LP usually appears as red, sore, or thinning patches or bumps that can cause burning or itching. It affects both men and women and can be mistaken for infections or other skin conditions.

How Is It Diagnosed?

Doctors usually diagnose lichen planus by looking at the typical appearance and symptoms. But if the case is unusual or mainly involves the mouth or nails, further tests might be needed:

KOH test: To rule out fungal infections;
Skin biopsy: A small sample confirms the diagnosis. Under the microscope, it shows thickening of the skin layers, damage to the base layer, and a band of immune cells at the junction between skin layers;
Blood tests: To check for causes like hepatitis C;
Review of allergies and medication history: Especially if a drug reaction is suspected.

Other Conditions That Can Look Similar

Some conditions that might be confused with LP include:

Psoriasis: Usually thicker patches with silvery scales and typical nail changes;
Pityriasis rosea: Starts with a single patch, then spreads in a “Christmas tree” pattern, and usually clears on its own;
Eczema or atopic dermatitis: Often more weepy with blisters and intense itching;
Cutaneous lupus erythematosus: Sensitive to sunlight, with scarring and positive autoimmune blood tests;
Drug-induced lichenoid reactions;
Fungal infections like ringworm or tinea versicolor: Confirmed by microscope examination.

Treatment

There’s no one-size-fits-all cure for lichen planus, but most cases improve on their own within months or a few years. Treatment focuses on relieving symptoms and preventing complications, especially when the mouth, scalp, or nails are involved.

Managing Symptoms and Medication:

Topical steroids: The first choice for treating skin and mouth LP;
Topical calcineurin inhibitors: Tacrolimus or pimecrolimus for sensitive areas like the face or genitals;
Oral antihistamines: To ease itching;
Light therapy: Narrowband UVB for widespread skin involvement;
Systemic treatment (for severe cases): May include oral steroids, retinoids (like acitretin), methotrexate, ciclosporin, or biologics if other treatments don’t work.

Treating Mouth and Genital Lesions:

Topical steroids or calcineurin inhibitors;
Good oral hygiene;
Avoiding irritants such as spicy foods, alcohol, and smoking.

Prevention and Advice for Patients

Avoid scratching, rubbing, or injuring affected areas;
Keep skin well moisturised to support its natural barrier;
Identify and reduce exposure to possible triggers like certain medicines or allergens;
Manage stress through behavioural or psychological support where possible;
People with oral LP should avoid smoking, alcohol, and spicy foods;
Regular check-ups are important for mouth LP because of the small risk of cancer, especially in erosive types.

Summary

Lichen planus is a complex, long-lasting inflammatory condition that can affect the skin, mucous membranes, nails, and scalp. While it’s not life-threatening, its symptoms and visible signs can cause real distress. Early diagnosis, managing symptoms, and personalised treatment help improve quality of life.

Most cases get better over time, but some forms—especially those affecting the mouth or scalp—need ongoing monitoring and specialist care.