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 true inflammatory croup, a very hot compress or sponge and steam-inhalation are especially to be recommended, and having been satisfied with these I have not often used the cold applications recommended by some authors.
In Spasmodic Croup, however, a cold wet cloth to the back of the neck and the larynx during the attack, and douching the spine or the whole body once or twice daily, is an effective treatment.
Liquor potassae has been used in croup both locally and internally. Certainly it will dissolve fibrinous membrane outside the body, and to some, but not to a great, extent may be available in the form of spray (1/2 or 1 dr. to 1 oz. of water). It has been compared to mercury in its constitutional effect of fluidifying secretion and of promoting absorption, but it acts too slowly to be depended upon for so acute a malady as croup. Iodide of potassium is more effective, and the acetate of potash seems to have sometimes acted well. The bichromate I have occasionally used locally and internally, with excellent effect, in true membranous croup.