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 the chronic stages of this complaint, where secretion is profuse and spasm severe, and there is not much complicating bronchitis or pyrexia, I have seen alum exert a very beneficial influence: 4 to 10 gr. in water or syrup should be given three or four times daily. Dr. Golding Bird introduced and highly commended this treatment, conjoining the alum with conium and dill-water. Dr. Meigs states that alum has given him, in sixty-eight cases, better results than any other remedy (Diseases of Children). Its good effect may be traced, probably, to a local astringent action on the fauces; hence it is best administered in some thick vehicle, and swallowed slowly.
Dr. Granville states, "without presumption," that in almost every case of whooping-cough this medicine, given early, removes the disease (p. 64), and Dr. Hamilton Roe, in a special treatise (1838), records equally excellent results. He was rather in advance of his time in concluding pertussis to be not always inflammatory, but "a nervous affection, having its seat in the mucous membrane of the bronchi and the pneumogastric nerve," and for the "nervous element," i.e., the peculiar whooping or spasmodic cough, he valued prussic acid more than opium, belladonna, or any other remedies then in use: he gave very full doses, such as 3/4 min. of Scheele's acid to infants, and 1 1/2 drop every quarter-hour for twelve hours to a child of ten years. I think this another illustration of the benefit to be obtained from the medicine when it may be justifiably and yet cautiously pressed, but for average practice it would be dangerous, and I agree with Sir T. Watson, who thinks the remedy in such doses "too gigantic for such young subjects;" also with Dr. C. West, who finds it "sometimes magical" for diminishing the frequency and severity of the paroxysm, but sometimes inert, sometimes poisonous. Dr. Atlee, judging from two hundred cases, gives a most favorable report of it (American Journal, vol. x.), and my own experience is decidedly in the same direction - the more purely nervous the paroxysms, the better will the remedy act, though some difficulty in graduating its dose will always remain: also, as is well known, the results obtained from remedies unaccountably vary in different epidemics and different individuals. In other forms of irritative cough, connected with spinal or vagus irritation, 1 have seen more benefit from this acid than from any ordinary sedatives; and the long-recognized clinical value of the drug in such conditions is of marked interest taken in connection with the special effect on the medulla and vagus, mentioned under physiological action.