It doesn't take stupid-hots to light up your hands!
I made a great vat of 5 pepper chili yesterday, chock full of chopped-up SW varieties, straight off the plant. Everything was warm to one degree on another, but nothing was more potent than Lumbre and (a lot of) Cayenne. Apart from a mild eye rub moment several hours later, I didn't think too much about it. After poking my eye, did wash my hands and soon went to bed.
Yikes! Around 2am, I awoke with my left hand all lit up. Tingling waves of heat roamed the thin skin on the back of my hand and fingers, concentrating in the cuticle area and places that were recently scraped or otherwise injured. Occasionally an entire finger would slowly warm up, feeling as if it was being immersed in very warm water. I won't call it outright painful, but it is somewhat uncomfortable. Multiple dish soap washes have helped the most, but there's still a bit of prickle left....
I lit up my forehead a few weeks ago, but it was a temporary, sorta-pleasant, experience. Somehow I never really realized that peppers could burn relatively thick skin. Glad to have learned this lesson with relatively mild varieties. I bet soaking your hands in moruga juice is an altogether different experience!
Edit:
24 hours later and I thought I was done with this little adventure. NOPE! A nice warm shower felt like fountaining lava when it hit my hand. The flamage lasted for an hour or so before slowly subsiding. My hand is still tingling a bit - letting me know that it's not yet forgiven my folly.