What Causes Fluid Filled Blisters On Both Elbows And Buttocks?

Hi I am having an outbreak of bright red bumps, some look fluid filled, around the inside of both elbows, outside of both elbows, butt, backside of both armpit areas, inner to back of thighs on both legs, pretty consisent to both sides of my body. What could this be? I have had this before multiple times. Many times it doesnt get this bad just usually around my elbows. Sometimes but not often it gets extreme. Once it has been all over my entire body from my neck to my thighs.