Dead organic matter, such as manure, is decomposed by microorganisms. These, however, are also dangerous for the hoof horn, as the dead corneous cells can be found on them, and thus also the dead organic matter.
Rainscald is caused by a bacterium belonging to the actinomycetes (Actinomycetales): Dermatophilus congolensis. The bacterium is a part of the normal microbial flora of the skin of many animals (sheep, goats, horses), and it is harmless to them.
This is how the use of EM is evaluated by Daniela Otto-Prins, a person professionally dealing with horses, having a lot of knowledge and loving horses. Daniela Otto-Prins has been applying EM for two years in her model stud.