Coconut oil
Thanks to its health oil and vitamin E content, it will keep your armpit moisturized, prevent itchiness and help the healing process of the area.
Apply it on your armpit and wait for the skin to absorb the oil. Repeat this a few times a day until the rashes disappear.
Alternatively, mix 4 spoons of coconut oil and 1 spoon of lavender oil, apply it on your armpit by using a cotton ball. Wait for 10-15 minutes and rinse with cold water. Dry thoroughly.