Lichen Simplex

Lichen simplex, also known as lichen simplex chronicus, is characterized by thickened and localized skin lesions that result from scratching in response to chronic itching. This chronic itching, also known as neurodermatitis, is often spontaneous and severe, prompting a strong desire to scratch. Scratching may lead to inflammation and further irritation. As the itch persists, scratching can become subconscious and repetitive, resulting in the “itch-scratch cycle.” The repeated scratching can lead to lichenification, the darkening and thickening of an area of skin. Commonly, lichen simplex occurs on accessible areas of skin, such as the head, neck, arms, hands, and genitals. 

Lichen simplex has been found to occur in up to 12% of the population. It has been diagnosed most frequently among females who are between 30 and 50 years of age.

Although the exact cause for lichen simplex is unknown, current data indicate that both emotional and environmental factors play roles. The psychological distress involved in anxiety disorders, depressive disorders, and obsessive-compulsive disorder may present physically as itchiness. Studies suggest that scratching may be a distraction from one’s internal thoughts. This combination of psychological, emotional, and physical factors may perpetuate the itch-scratch cycle in an individual.

Regarding environmental factors, excessive heat, sweat, and dry air can cause itchy skin. The use of some cleansers, detergents, and scented products may also induce skin irritation. Moreover, lichen simplex may be secondary to other skin disorders, such as atopic dermatitis, seborrheic dermatitis, contact dermatitis, or psoriasis. 

Lichen simplex appears as scaly, dry patches of skin in easily accessible areas, such as the hands, arms, head, neck, and genitals. Over time, these patches can become a yellow or brown color that doesn’t match the rest of the individual’s skin tone, and they vary in size based on how much skin is impacted by the repetitive scratching. Lichenified skin is thickened and leathery with exaggerated skin lines. The body produces thickened skin to protect itself from the chronic scratching and rubbing. 

 Under a microscope, lichenified skin is marked by hyperkeratosis and epidermal hyperplasia, which appear as an overgrowth and thickening of the epidermis layers (i.e., the outermost surface of the skin). 

Diagnosis of lichen simplex chronicus may start by asking the individual about their medical and family history. A physical exam will then allow the clinician to take a close look at the affected area, which may prompt the clinician to recommend additional testing to rule out other skin conditions. 

A patch test may be performed to rule out an allergic reaction, which can cause similar inflammation of the skin, by analyzing skin reactions from contact with potential allergens. In some cases, a skin biopsy can be used to exclude the presence of other skin diseases, like psoriasis, in which skin cells grow faster than expected; mycosis fungoides, a type of blood cancer; or squamous cell carcinoma, a skin cancer. Additionally, blood cultures can help rule out involvement of possible pathogens, like the fungi that cause jock itch (i.e., tinea cruris) or yeast infections (i.e., candidiasis). 

There are a variety of ways to treat lichen simplex. Anti-inflammatory medications such as topical steroids can be prescribed to reduce itching and inflammation. Topical salicylic acid, which can loosen the thickened skin, may also be prescribed. The individual may try covering the affected skin area so that it becomes less accessible and more difficult to scratch. If the area has become infected, a healthcare professional may prescribe antibiotic treatment. 

If the inflammation seems to be an allergic reaction to an environmental allergen, antihistamine medication may help manage the reaction. In this situation, a healthcare professional may advise the individual to reduce exposure to the allergen. 

For severe cases, therapeutic exposure to UV light (i.e., phototherapy), inflammation-treating immunomodulatory medications (e.g., tacrolimus), or application of extreme cold to remove lichenified skin (i.e., cryosurgery) may be recommended. In rare instances, lichen simplex can lead to squamous cell carcinoma or verrucous carcinoma, which would require long-term monitoring of the affected areas.

Due to the links between lichen simplex and psychological disorders, an individual may consider consulting a mental health professional to address the emotional stress that may lead to continued itching.