You see, people, THIS is what happens if you decide that sunscreen is not an important part of your kit. That was the second worst sunburn of my life, and after the first*, you'd think I'd have learned my lesson. See, I can't stand the feel of sunscreen on my skin. It feels like bugs crawling on me, and it's gross. The same goes for bug spray, but that's another story. Anyway, because I don't learn from my mistakes, the above pictured burn, while not as bad, was gotten in some of the colder weather I've experienced while in historical clothing. It was May in Northern Michigan, which still regularly sees temperatures in the forties and fifties, and with a brisk wind blowing, it made sense to sit in the sun to keep warm. Lesson: even when the temperature belies it, the sun's rays are still hazardous.
The damage from that particular burn was deep and lasting, too. It took almost a whole year for the last traces of the tan from it to disappear, and I could see a noticeable deepening in the nasolabial folds--smile lines--between my mouth and nose. My skin lost some of its elasticity and was more prone to irritation, too. This was four years ago now, and the damage is mostly healed, but it took time and I've been extra-careful of my skin ever since.
Since then, I've done much better. (Honest.) I'm blessed with fairly olive skin, which, while it means I'll never have the ideal porcelain complexion of yesteryear, also means that I can use a fairly mild sunscreen to prevent disasters like that train wreck above. My daily facial lotion of choice is SPF 15, though it's also available in SPF 30 for those of you with lovely fair skin. I actually usually buy the generic version, but the principle is the same. I like this stuff for not-just-facial use because it's lightweight and doesn't leave that nasty feeling behind.
So long story short: Reenacting is fun. Being outside is fun. Don't be stupid and make it not fun by getting an awful sunburn. Use protection! (What, like you haven't heard that before?) There is no shame in using SPF 50 or 60. Someday, your skin will thank you.
*The absolute worst burn I ever got was during a canoe trip where I spent all day out on open water in an aluminum canoe with no sunscreen on at all. I spent the next two weeks peeling, with the highlight being my arms--the flakes were the size of post-it notes. Disgusting. After that, you'd think I would have learned!