Calamine lotion has been the go-to solution for inflamed and itchy skin for decades. Your grandparents used it, your parents reach for it, and you probably have a bottle of it tucked away somewhere.

If you’re in your 40s or older, you might have memories of having chickenpox—the once-common childhood virus was a rite of passage that usually involved a week of itchy fluid-filled blisters, lots of ...