Ted Rosen, MD, began his lecture on itchy dermatoses by defining itch as “the unpleasant sensation which evokes the desire to scratch.” While histamine can be a major driver of itch, there are numerous others including neuropeptides, proteases, cytokines, substance P, therefore, it is important to consider the addition of other agents beyond antihistamines to control itch. When Dr. Rosen approaches the patient with itch, he categorizes these patients as those with rash and those without rash as well as those with an identifiable diagnostic etiology and those with no known identifiable diagnostic etiology.
Rosen was among a stellar lineup of expert dermatologists and dermatology PAs who addressed an attentive audience at the SDPA 21st Annual Fall Dermatology Conference in Nashville, Tennessee, Oct. 25-29, 2023.
One of the most common causes of itch is xerosis cutis. This is more common in elderly patients and exaggerated in the winter. Dry skin can be recognized by xerotic eczema or eczema craquele. Moisturizing can help with xerosis cutis, but it is important to understand the differences between humectants, emollients, occlusive agents and ceramides. Dr. Rosen recommends ensuring patients use ceramide rich moisturizers as they work best. It is important to rule out medical causes of itch including diabetes (insipidus and mellitus) and hypothyroidism. In patients who present with an itch and no rash, systemic disease is the cause 13-22% of the time. These patients should be evaluated for renal failure, hepatic failure, biliary obstruction, thyroid dysfunction, sprue, cancer, HIV, GI parasites, lymphoma and iron deficiency. When evaluating these patients, medications the patients have started within the last month should be considered.
In the evaluation of a patient with itch, scabies should be on the differential with careful attention to examination of the fingerwebs, glans penis, areola and the wrists. If you cannot scrape or find a mite, you can treat upon intuition. Options for treatment include oral ivermectin or topical permethrin 5%. Both of these treatments need to be repeated 1-2 weeks after the initial treatment. When evaluating the patient who presents with an itchy head, ensure to check for head lice. While this used to be most common in children, it is becoming more prevalent in adults likely due to our cultural habit of taking “selfies.” A newer treatment option for lice is the prescription spinosad. Additional treatments for lice include wet combing, manual nit removal, lice clinics and high heat.
Additional considerations in the differential diagnosis of the itchy patient include fungus, psoriasis, atopic dermatitis, lichen planus and insect bites. The itch of psoriasis is worsened by stress, heat and sweating. Dr. Rosen reports a helpful treatment for the relief of itch in the psoriatic patient is 2 full-sized aspirin throughout the day. When evaluating patients with insect bites, Dr. Rosen reports severe and very itchy insect bites may be a sign of an occult hematologic malignancy such as chronic lymphocytic leukemia. Additional conditions discussed in this lecture included pruritic urticarial papules and plaques of pregnancy, scabies incognito, prurigo nodularis, eosinophilic folliculitis and treatment options for the persistently itchy patient.
Byline: Sarah B.W. Patton, MSHS, PA-C