A wide range of conditions cause rashes, some common and others quite rare. One of the more unusual types of rashes is caused by a disease called lichen planus. Lichen planus causes an itchy rash made up of shiny red and purple bumps, and patches of raised, sometimes rough, skin. Other symptoms of the condition may include mouth sores, fingernail splitting, and hair loss.

Lichen planus is thought to be caused by the body’s own immune system. And though it can occur in people of any age, lichen planus is rare in children. It is most common in people between the ages of 30 and 60.

“We have many different treatments for lichen planus, from topical steroid creams or local injections to systemic medications, such as pills or injections, to light therapy. The best treatment or combination of treatments depends on each patient’s skin rash, symptoms and other medical issues,” says Yale Medicine dermatologist Alicia Little, MD, PhD. “If you have lichen planus, the treatment options that may help you can be best identified by your board-certified dermatologist.”

Lichen planus is an inflammatory disease that most commonly affects the skin and mouth, but can also affect the esophagus, genitals, nails, and scalp. When it affects the skin, it usually causes an itchy, inflamed rash. In the mouth, the disease is characterized by the development of white, lace-like patches on the tongue and cheeks, sometimes accompanied by painful sores.

Researchers don’t know exactly what causes lichen planus, but it is widely thought to be the result of an abnormal immune response in which the body’s immune system attacks and damages healthy skin cells called keratinocytes.

• Genetic factors may play a role in the disease: There is some evidence that lichen planus can run in families and certain genes have been associated with it.

• Environmental exposures are also known to trigger rashes and other symptoms of lichen planus. Various prescription drugs have been associated with lichen planus flares, such as some high blood pressure medications, antimalarial medications, and certain antidepressant and anti-anxiety medications. However, for most patients with lichen planus, the rash is not caused by a medication, even prescription ones. Patients should always talk with their dermatologist and prescribing physician before discontinuing any prescription medication. In rare cases, metallic dental fillings may also cause symptoms to emerge, and hepatitis B and C infections have been linked to the disease. 

The symptoms of lichen planus vary depending on the area of the body affected.

Skin. The skin is the most commonly affected organ. Symptoms include:

• Rash of red or purple, flat-topped, shiny bumps (papules) that, over time, may form into larger patches of raised, rough skin called plaques, ranging in size from a few milimeters to 1-2 centimeters. In patients with darker skin colors, bumps may be dark violet or gray, while patients with lighter skin colors often have bumps that are more pink or light purple.
• Itchy rash
• White lines known as “Wickham’s striae” may appear on the surface of papules and plaques.
• When the rash recedes, it may leave behind dark spots on the skin.
• The rash most frequently affects the wrists, lower legs, lower back, or genitals.

Mouth. In about 50% of cases, lichen planus affects the mucous membrane lining of the inside of the mouth. Symptoms include:

• Wickham’s striae on the tongue and cheeks, and—less frequently—in the esophagus
• Sores on gums, which may be painful enough to cause difficulty eating and drinking

Nails. Around 10% of cases involve the fingernails or, less frequently, the toenails. Symptoms include:

• Development of ridges on nails
• Splitting
• Nail may loosen or separate from the nail bed
• Outer edges of nail may recede, leaving a thin nail (called “lateral thinning”)

Scalp. A type of lichen planus, called lichen planopilaris, may affect the scalp. Symptoms include:

• Small, scaly pink, violet, or red bumps around the hair follicles on the scalp, which may be itchy
• Hair loss (which is usually permanent)

Genitals. Lichen planus can affect the genitals of men and women. On the skin, a rash of flat-topped papules, red or purple in color, may appear on the head of the penis or the clitoral hood and inner labia. In women, lichen planus may cause sores in the vulva and vagina that can be painful and, if untreated, can result in scarring.

Often, your doctor will be able to diagnose lichen planus based on a physical examination of your skin, nails, scalp, and mouth. He or she may ask whether you take any medications known to trigger lichen planus.

To confirm the diagnosis and rule out other possible causes of the rash, your doctor will usually need to perform a skin biopsy. In this procedure, the doctor removes a small piece of skin tissue. 

There are two primary techniques for taking skin biopsies: One involves a “punch” biopsy, in which a tiny cylinder of skin is removed with a special tool. The other is a “shave” biopsy, in which the top layers of a small area of skin are removed using a razor. A pathologist then examines the tissue under a microscope to check for characteristic signs of lichen planus.

While there is no cure for lichen planus, many treatments can reduce the rash and alleviate the itching caused by the condition. In many cases, the condition eventually goes away, without treatment, six months to two years following its onset.

Treatments that may help control symptoms include:

• Corticosteroids. Corticosteroids can reduce inflammation and relieve itching. For localized rashes, your doctor may prescribe a lotion or ointment. Steroid rinses, pastes, and gels may be used to treat oral symptoms. For more severe cases, steroid injections or oral corticosteroids may be necessary.
• Phototherapy. Exposing affected areas of skin to specific wavelengths of ultraviolet light can reduce inflammation and itch.
• Retinoids. Oral retinoids, like isotretinoin and acitretin, may be prescribed for lichen planus.
• Immunosuppressants. Because of the involvement of the immune system in lichen planus, immunosuppressants—medications that suppress the immune system such as methotrexate and cyclosporine, among others—are sometimes prescribed to treat more severe cases. beh

In addition to taking medications prescribed by a physician, people who have oral lichen planus should follow a good oral hygiene routine that includes regular flossing and brushing, as well as regular visits to the dentist.

Usually lichen planus clears up on its own within two years of onset—but for some, particularly when there is oral, vaginal, or nail involvement, the condition lingers longer and may sometimes recur. Depending on the severity of the rash, lichen planus can cause scarring.

Also, lichen planus that causes sores in the mouth or that affects the genitals has been associated with a slightly higher risk of oral cancer and squamous cell carcinoma of the genitals, respectively. In these cases, a doctor can provide information about screening options.

“While the diagnosis can seem overwhelming to a patient with lichen planus, your dermatologist will be well-versed in its treatment options,” says Dr. Little. “Your dermatologist will work with you to answer your questions, address your symptoms, and make sure the therapies selected are the right ones for you.”