This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
In this, which is a catarrhal form of disease, arsenic has not so large a measure of success as in the last mentioned; still it is often very useful, and especially in combination with other remedies. Acute cases not only receive no benefit, but I have seen them much aggravated by it; the proper period for its use requires, therefore, careful consideration. It is very suitable in scaly - which are of necessity rather chronic stages, and have received the distinct name of "eczema squamosum"- in superficial subacute forms with moderate infiltration, and in cases with persistent irregular patches about the scrotum, anus, or vulva (Rayer), or about the hands or fingers (Duhring). Sometimes the later stages of a chronic infantile eczema seem much benefited by the addition of the drug to iron or cod-liver oil, and sometimes an infant has been successfully treated by arsenical medication through the mother (Begbie, Anderson). The last-named observer, in his excellent special treatise, estimates the value of arsenic highly: he points out, as others have done, that children will readily bear a proportionately large dose; at the same time, he notes that there is much tendency to "catching cold," or even bronchitis, during an arsenical course, also he insists on the necessity for its prolonged continuance. Mr. Erasmus Wilson considers that the treatment of eczema resolves itself into that of "debility," and advocates the use of ar-senic "as a nerve-tonic and stimulant to cutaneous function;"' and generally combines it with a non-astringent preparation of iron, as the vinum. My own use of arsenic in ordinary eczema is rather the exception than the rule, and I am much in accord with Dr. Piffard, who, after calling this mode of treatment "empirical, as opposed to rational," and quoting the prevalent opinion, "that if only sufficient of the remedy be used, the eruption must yield," states that, in his experience, it sometimes does harm and at other times has no influence, though in a minority of cases will give brilliant results: these may be hoped for in the dry scaly stages when extensive tracts of surface are affected ("On Skin Diseases," 1870); I would add, and when there are persistent patches oh the pudenda or extremities, as already described.