Anybody else experience this??

Back story, one of the ways I found out I was pregnant I had experienced burn like areas in my armpits and my hair line was excessively dry. I’ve been using the same body wash & deodorant for YEARS, so that was ruled out. Weird thing is the burns & dandruff went away once I hit my 3rd trimester.. Currently 5 months post partum and for some reason the burn marks are back?? Not pregnant nor change in soap or deodorant. What could it be?!?