There's a recipie for a hair rinse made out of borax water and apple cider vinegar that should help you along your way, both clean the infection well by soaking into the subdermis.
Generally it's 1 teaspoon borax to 1 liter warm distilled water, but for skin you can go 1 tablespoon to .5 liters (2 cups) warm water. 1 cup or more of apple cider vinegar, and then try it with a wet washcloth on your armpit. The skin is similar to the porosity of the intimate areas, might be a good way to test first.
Almond oil can help provide what's needed to inhibit regrowth for a period of time.
I love that stuff. <3