This sounds like a form of eczema, not herpes or any other STD. Best not to pop the blisters. I don't think you need to worry about the pre-existing condition aspect of things, because eczema by its nature fluctuates on and off over years. For peace of mind, and treatment if needed, you're wise to get a definitive diagnosis in person sooner rather than later. The cause of this eczema (called dyshidrotic) is unknown, but it's not allergic or contagious. Check it out.
Best.
Dr. Rockoff