Used Teatree Oil Under Arm On A Skin Tag. Rash Spreading To Side And Back. Try Benadryl?

I used tea tree oil topically under my arm for 4 weeks on a skin tag. After 4 weeks a small rash occurred under my arm. I put cortisone on it to help with the mild itchiness. I then tried Neosporin on it, which just made it worse. It is now spreading down the underside of my arm, my side and my back. The itching remains mild, doesn t disrupt sleep and seems to get worse when I m wearing long sleeves. Was going to try some Benedryl next to see if it would calm it down.