Erythema infectiosum, fifth disease, or slapped cheek syndrome is one of several possible manifestations of infection by parvovirus B19. Fifth disease typically presents as a rash and is more common in children. While parvovirus B19 can affect humans of all ages, only two out of ten individuals will present with physical symptoms.The name "fifth disease" comes from its place on the standard list of rash-causing childhood diseases, which also includes measles (first), scarlet fever (second), rubella (third), Dukes disease (fourth, but is no longer widely accepted as distinct from scarlet fever), and roseola (sixth). Treatment is mostly supportive. Signs and symptoms
Fifth disease starts with a low-grade fever, headache, rash, and cold-like symptoms, such as a runny or stuffy nose. These symptoms pass, then a few days later, the rash appears. The bright red rash most commonly appears in the face, particularly the cheeks. This is a defining symptom of the infection in children (hence the name "slapped cheek disease"). Occasionally, the rash will extend over the bridge of the nose or around the mouth. In addition to red cheeks, children often develop a red, lacy rash on the rest of the body, with the upper arms, torso, and legs being the most common locations. The rash typically lasts a few days and may itch; some cases have been known to last for several weeks. Patients are usually no longer infectious once the rash has appeared.Teenagers and adults may present with a self-limited arthritis.
Butenafine, sold under the brand names Lotrimin Ultra, Mentax, and Butop (India), is a synthetic benzylamine antifungal. It is structurally related to synthetic allylamine antifungals such as terbinafine. Medical uses
Butenafine is indicated for the topical treatment of tinea (pityriasis) versicolor due to Malassezia furfur, as well as athletes foot (Tinea pedis), ringworm (Tinea corporis) and jock itch (Tinea cruris) due to Epidermophyton floccosum, Trichophyton mentagrophytes, Trichophyton rubrum, and Trichophyton tonsurans. It also displays superior activity against Candida albicans than terbinafine and naftifine. Butenafine demonstrates low minimum inhibitory concentrations against Cryptococcus and Aspergillus. There is some evidence that it is effective against dermatophyte infections of the toenails, but needs to be applied daily for prolonged periods (at least one year). Typical usage
For 1% cream:

for adults and children 12 years and older:
wash the affected skin with soap and water and dry completely before applying
apply once a day to affected skin for 2 weeks or as directed by a doctor
wash hands after each use
children under 12 years: ask a doctor

Available forms
Butenafine is typically available as a 1% topical cream. Pharmacology
Like the allylamine antifungals, butenafine works by inhibiting the synthesis of ergosterol by inhibiting squalene epoxidase, an enzyme responsible for the creation of sterols needed in fungal cell membranes. Lacking ergosterol, the cell membranes increase in permeability, allowing their contents to leak out. Furthermore, inhibition of squalene epoxidase leads to a toxic buildup of squalene. This double action of butenafine (increased membrane permeability and toxic buildup of squalene) makes butenafine fungicidal rather than merely fungistatic.