Crotamiton Health Dictionary

A skin disorder typi?ed by a bran-like desquamation (?aking). There are several varieties including P. alba, rosea, versicolor (fungal caused) and rubra (exfoliative dermatitis).

Pityriasis alba is a mild form of chronic eczema (see DERMATITIS) occurring mainly in children on the face and in young adults on the upper arms. It is characterised by round or oval ?aky patches which are paler than the surrounding skin due to partial loss of MELANIN pigment. The appearance is more dramatic in dark-skinned or suntanned subjects. Moisturising cream often su?ces, but 1 per cent HYDROCORTISONE cream is more e?ective.

Pityriasis rosea is a common self-limiting eruption seen mainly in young adults. It usually begins as a solitary red ?aky patch (often misdiagnosed as ringworm). Within a week this ‘herald patch’ is followed by a profuse symmetrical eruption of smaller rose-pink, ?aky, oval lesions on the trunk and neck but largely sparing the limbs and face. Itching is variable. The eruption usually peaks within 3 weeks and fades away leaving collarettes of scale, disappearing within 6–7 weeks. It rarely recurs and a viral cause is suspected but not proved. It is not contagious and there is no speci?c treatment, but crotamiton cream (Eurax) may relieve discomfort.... pityriasis

A common contagious itching disease caused by Sarcoptes scabei hominis (see SARCOPTES) which can live only on human skin. The fertilised female burrows into the skin surface, creating a tunnel within the stratum corneum in which she deposits 2–3 eggs per day, as well as faecal pellets which contain the ALLERGEN which initiates the immune reaction responsible for symptoms. The adult female is just visible. Eggs hatch within 3–4 days, producing larvae. After successive moults these become adult mites and the 15-day lifecycle re-starts. A rapid build-up of mite numbers is not noticed by the host until an immune response induces itching after about six weeks. Subsequently, scratching reduces the adult mites to a dozen or fewer. Scabies is spread by skin-to-skin contact, usually via the hands: it thus spreads in a family or sexual setting. Though most common in young adults, scabies can affect any age-group.

Typically the patient complains of widespread severe itching, worse when the body is warm after a bath or in bed. Burrows are visible as wavy black lines 3–5 mm long in the skin of the hands, wrists or sides of the feet. The intensity of the rash depends on the immune response. Papules, pustules, crusts and excoriations are seen on the hands and there may be a widespread eczematous (see DERMATITIS) or urticarial (see URTICARIA) rash elsewhere. Papules or even nodules on the PENIS and SCROTUM are characteristic. In infants, burrows occur on the palms and soles. Diminished immune response in old age, DOWN’S (DOWN) SYNDROME, etc. lead to a type of scabies which is less itching and more scaly. Rarely, absence of immune response causes a mite-saturated, generalised scaly dermatitis (Norwegian scabies). Admission of such a patient to hospital may result in an outbreak of scabies in other patients, sta? and visitors caused by mite-infested airborne scale.

Treatment MALATHION 0·5 per cent aqueous lotion, or PERMETHRIN 5 per cent cream, applied to the whole body, except the head, for 24 hours and then washed o? cures the infection. In infants the head and neck should be included. The secondary eruption may take 2– 3 weeks to settle completely and 10 per cent crotamiton cream is used during this period. It is essential that all intimate contacts be treated simultaneously. FOMITES need not be treated.... scabies

n. an agent that relieves itching (*pruritus). Examples are *doxepin and *crotamiton, applied in creams or lotions, and some *antihistamine drugs (e.g. *alimemazine), used if the itching is due to an allergy.... antipruritic