I have used it as a deodorant for years, as traditional antiperspirants gave my skin severe irritation. Antiperspirants contain aluminum chloride, the harmful chemical.I don't have the Osma but i do have a Gentleman Jon block that i like and use once in a while. I would use Alum more often but im concerned about health issues with taking aluminum in through the skin. Is that concern valid or am i worried about nothing.
The alum block is made of potassium alum, a salt mineral.
According to the National Library of Medicine,
Aluminum potassium sulfate - https://pubchem.ncbi.nlm.nih.gov/compound/Aluminum-potassium-sulfate
"Potassium alum is considered by the FDA as a generally recognized as safe (GRAS) substance. It is an inorganic salt, also called potassium aluminum sulfate"