In response to the enquiry: “Is it normal for baking soda to sting on foot fungus?”
Baking soda stings when applied to moist areas infected by the tinea family of fungi.
That would include athlete’s foot that is moist between the toes and is infected by the tinea pedis.
It also stings when applied to the moist groin and crotch area infected by crotch itch, or tinea cruris.
Hydrogen peroxide applied to the moist groin area stings a lot, but when one soaks athlete’s foot in it, the foot does not really sting that much. Instead, foaming occurs from between the toes where the tinea pedis infection is.