Lichen Simplex Chronicus
Lichen simplex chronicus is chronic, itchy inflammation of the top layer of the skin.
Lichen simplex chronicus is caused by chronic scratching of an area of skin. The act of scratching triggers more itching, beginning a vicious circle of itching-scratching-itching. Sometimes the scratching begins for no apparent reason. Other times scratching starts because of a contact dermatitis, parasitic infestation, or other condition, but the person continues to scratch long after the inciting cause is gone. Doctors do not know why this happens, but psychologic factors may play a role. The disorder does not seem to be allergic. It usually develops between the ages of 20 and 50.
Lichen simplex chronicus can occur anywhere on the body, including the anus (see Pruritus Ani) and the vagina (pruritus vulvae—see Genital Itching), but is most common on the upper chest or back, arms, neck, and legs. In the early stages, the skin looks normal, but it itches. Later, dryness, scaling, thickening, and dark patches develop as a result of the scratching and rubbing.
Doctors try to discover any possible underlying allergies or diseases that may be causing the initial itching.
When the disorder occurs around the anus or vagina, the doctor may investigate the possibility of pinworms, trichomoniasis, hemorrhoids, discharge, fungal infections, warts, contact dermatitis, or psoriasis as the cause.
For the disorder to clear up, people must stop all scratching and rubbing of the area. Standard treatments for itching should be followed. Applying surgical tape saturated with a corticosteroid (applied in the morning and replaced in the evening) helps relieve itching and inflammation and protects the skin from scratching. For small areas, the doctor may inject longer-acting corticosteroids under the skin to control the itching. Doctors may give antihistamines by mouth.
When this disorder develops around the anus or vagina, the best treatment is a corticosteroid cream. Zinc oxide paste may be applied over the cream to protect the area. This paste can be removed with mineral oil.