Scalp Pruritus: Itching for Treatment Part 2



Scalp pruritus has a variety of sources (Figure 1). Part 1, published in the September 2017 issue of The Dermatologist, discussed inflammatory dermatologic disorders. Part 2 addresses common infectious dermatologic disorders, neuropathic, systemic, and psychogenic disorders (Table). 

Dermatologic Infections

Tinea capitis is a dermatologic infection caused by dermatophytes.1,2 Although tinea capitis can affect any person, it predominately affects children of African descent.1,2 The main culprit is Trichophyton tonsurans that causes itching and scaling initially, and eventually can evolve to patchy alopecia with black dots or hair-colored dots (due to broken hair shafts).1,2 Gray circular patches with scale, diffuse scale, or diffuse pustules are also possible presentations.2 In severe cases, the infection sites may coalesce into boggy plaques with pustules that are tender called kerions.1 Cervical and suboccipital lymphadenopathy occurs frequently, but is not diagnostic.1,2 

tableA potassium hydroxide preparation might not be necessary with a classic presentation, but is useful if the diagnosis is unclear.1 T tonsurans is found within the hair shaft under the microscope.1 If tinea capitis is diagnosed, then close contacts (such as young children in the same household) should be screened.2 Hair combs, brushes, towels, and other potential fomites should be sterilized to reduce reinfection or spreading disease.2 
The treatment requires systemic antifungals due to poor penetrance of topical agents into hair follicles.1 Terbinafine and fluconazole can be used as first-line treatments.1,3 A baseline liver panel and complete blood count may be acquired before starting treatment in patients with known liver damage or concomitant medications that are cleared through the liver. Griseofulvin and itraconazole are also potential alternatives.1,3 Although terbinafine, itraconazole, and fluconazole may be superior in treating tinea capitis caused by T tonsurans, griseofulvin may be more cost-effective.3 Griseofulvin is also superior to terbinafine for disease caused by Microsporum species.3 Treatment length varies based on the drug used, but lasts for several weeks.1 If kerion is present, then prompt antifungal treatment coupled with topical steroids is necessary to avoid permanent hair loss.2 Selenium sulfide or ketoconazole shampoo can be added as adjuvant therapy to expedite treatment and to prevent reinfection through causative spores.3 
Pediculosis capitis is another infectious source of scalp pruritus (Figure 2).4-6 In developed nations, the disease is generally limited to children, but can occur at all ages.4 Infections often arise in the form of an epidemic.4 Head lice feed on human hosts exclusively.4 Severe pruritus usually develops 1 to 4 weeks after infection, but not every case develops pruritus.4 The itching is through an allergic sensitization response.5 An important aspect of pharmaceutical treatment to consider is if the treatment is ovicidal. If the treatment is not ovcidal, then a second treatment is necessary after 8 days.5 Topical pediculicides’ efficacy such as malathion and permethrin has waned in recent years due to resistance.4-6 Spinosad is a new pediculicide antagonizing gamma-aminobutyric acid receptors demonstrating success after single treatment.4,6 Dimethicones are synthetic silicone oils that physically seal the lice breathing apparatus and still possess efficacy.5 Combination dimethicone therapy has up to 97% efficacy.4,5 Both topical and oral ivermectin are effective with a single treatment.4-6 Topical ivermectin can be used in children aged >6 months.4 Oral ivermectin is approved for individuals aged >5 years and weigh more than 15 kg.4,5 Pregnancy and breastfeeding are contraindications.5 Wet combing is a technique that can offer both diagnostic and therapeutic value.4,5 Wet combing should be done every 3 days until 4 consecutive “clear” combings.5 Infested or exposed clothing, combs, and bedding should be washed in hot water to kill lice.5,7 If other family members or children in a group setting need treatment, then the course should be synchronized to minimize reinfesation.4,5
Scabies of the scalp is a condition associated with children aged <2 years, and almost always younger than <15 years.8 Permethrin 5% cream is the treatment of choice for infants and children due to overall efficacy and safety.9-11 Malathion can also be used, but needs physician monitoring for children younger than 6 months.9 Clothing, sheets, and other linens should be washed in hot water >60°C and heat dried, or isolated in a plastic bag for 3 days to remove oxygen.12 
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