Or it may be used in liquor gutta-perchæ (traumaticin), a drachm to the ounce. It may also be employed in chloroform, a drachm to the ounce; this is painted on, the chloroform evaporating, leaving a thin film of chrysarobin; over this is painted flexible collodion. If the patches are few and large, chrysarobin rubber-plaster may be used.
Chrysarobin is usually rapid in its effect, but it has certain disadvantages; it may cause an inflammation of the surrounding skin, and, if used near the eyes, may give rise to conjunctivitis. As a rule, it should not be employed about the head. Moreover, it stains the linen permanently and the skin temporarily.
Pyrogallol is valuable, and is employed in the same manner and strength as chrysarobin. In collodion it should at first not be used of greater strength than three to four per cent., as in this form pyrogallol sometimes acts with unexpected energy. It is less rapid than chrysarobin, but it rarely inflames the surrounding integument. It stains the linen a light brown, however, and is not to be used over an extensive surface for fear of absorption and toxic effect. Oxidized pyrogallic acid, a somewhat milder drug in its effect, has been highly commended, and has the alleged advantage of being free from toxic action.
Tar is, all things considered, the most important external remedy. It is comparatively slow in its action, but is useful in almost all cases. As employed usually it is prescribed in ointment form, either as the official tar ointment, full strength or weakened with lard or petrolatum. It may also be used as pix liquida, with equal part of alcohol. Or the tar oils, oil of cade (ol. cadini), and oil of birch (ol. rusci) may be employed, either as oily applications or incorporated with ointment or with alcohol. Liquor carbonis detergens, in ointment, one to three drachms to the ounce of simple cerate and lanolin is a mild tarry application which is often useful. In stubborn patches an occasional thorough rubbing with a mixture of equal parts of liquor carbonis detergens and Vleminckx's solution, followed by a mild ointment, sometimes proves of value. In whatsoever form tar is employed it should be thoroughly rubbed in, once or twice daily, the excess wiped off, and the parts then dusted with starch or similar powder.
Ammoniated mercury is applied in ointment form, twenty to sixty grains to the ounce. Compared to other remedies it is clean and free from staining, although, as a rule, not so uniformly efficacious. It is especially useful for application to the scalp and exposed parts. It should not be used over extensive surface for fear of absorption.
β-Naphthol and resorcin are applied as ointments, thirty to sixty grains to the ounce, and as they are (especially the former) practically free from staining, may be used for exposed surfaces.
Gallacetophenone and aristol also act well in some cases, applied in five- to ten-per-cent. strength, as ointments.
In obstinate patches the x-ray may be resorted to, employing it with caution and in the same manner as in other diseases.
Pityriasis Rosea.
(Synonym: Pityriasis Maculata et Circinata.)