Native Deodorant

I switched over to the aluminum free native deodorant about 2 months ago, it worked great the first few weeks. .. Weeks go by and my armpits were turning a darker skin color than the rest of my body. They were irritated, and always like brownish. I'm pale white so it was really odd.. last night I stopped using it and used some of my boyfriends deodorant that he had in the closet because he doesnt like it.. I also used it all day today. Got out of the shower tonight and my armpits are back to normal... after about a month of being discolored. Does anyone know what could have caused this.. ??