In scabies (itch) it is the best remedy, killing the male parasite, which remains on the surface of the skin.
(It is fair to say that these views were published in one of his later works.) In treatment of disease Hahnemann rejected entirely the notion of a vis medicatrix naturae, and was guided by his well-known principle 1 The itch (scabies) is really an affection produced by the presence in the skin of a species of mite (Acarus scabiei), and when this is destroyed or removed the disease is at an end.
The fungus, Sorosporium scabies, which is the cause of the scab, does not penetrate into the flesh of the tuber, nor detract from its edible properties.
Similar spots are produced on potatoes in America by the fungus Oospora scabies, and in both cases, if affected "seed" potatoes are steeped in a solution of 2 pint formalin in 15 gallons of water for two hours before planting, the attack on the resulting crop is materially lessened.