Lichenoid dermatitis is an allergy that forms on the skin and causes a purple, itchy rash. It is caused by damage to the epidermis, which results in inflammation and problems with how the outer layer of skin interacts with the next inner layer of tissue, called the dermis. The condition is also known as lichen planus and most commonly results in lichenoid mucositis, a condition in which white lesions, blisters and ulcers form in the mouth. It does not usually affect children or young adults.
An uncommon condition, lichenoid dermatitis is easily diagnosed because of the purple tint of the polygonal papules, or raised bumps, that form on the skin. The rash usually forms on the ankles, lower back, wrists or forearms. It can also appear on the scalp, nails or genitals. The bumps can be anywhere from small, tiny dots to larger discs that can turn into scaly patches of skin that are itchy or uncomfortable. The rash can also appear as a line on parts of the body and often a gray discoloration of the skin results once the rash has disappeared.
It is believed that the problem is caused by an allergic reaction to medication or other chemicals, or that it develops as a result of a viral infection. Many heart disease, high blood pressure, hypoglycemic and arthritis medications are believed to cause an allergic reaction. Proton pump inhibitors have also been known to cause it.
While lichenoid dermatitis is not contagious, it can indicate a more serious skin condition, or could be caused by hepatitis C or graft-versus-host disease of the skin. A person with symptoms of this type of inflammation should immediately consult a medical professional to determine the cause of the rash and to develop a treatment plan. Usually, the skin will heal naturally within two years, but it can suddenly reoccur.
A healthcare professional can prescribe cortisone lotions or foams to treat the rash, but a patient will need to avoid the chemical substance that initially caused the irritation. Antihistamines for inflammation or antibiotics for an infection are also commonly prescribed. Depending on the severity of the rash, a medical professional may suggest steroid injections or photochemotherapy light treatments. These treatments will only help with the itching or look of the rash, however, and will not cure the skin condition.