What a name, huh?
The past couple vacations we've been on to Hawaii and St. Martin I've gotten this really weird rash. It itches and always appears on the inside of my arms and legs (areas not usually exposed to sunlight) after a couple of days. I thought it was heat rash for about three years. A couple weeks ago I was looking online about heat rash to see if there's any way to prevent it (strange herbs, etc.) since we're going to Grand Cayman soon. I found out I didn't have heat rash, which occurs when sweat gets trapped underneath the surface of the skin (I didn't sweat that much) but had this other weird skin thing called polymorphous light eruption (commonly called sun poisoning).
So pretty much I'm allergic to the sun. Well, not really. PMLE is actually a hyper-sensitivity to the sunlight and it can be developed (I never got it the very first time I went to Hawaii). Fortunately, it does not cause cancer or mean I am more likely to get cancer. In fact, I'd say it helps lower my chances of cancer, since it forces me to stay out of the sun and wear super-intense sunscreen. It's most common in (1) women (2) under the age of 30 who (3) live in northern climates and (4) take oral contraceptives. Check, check, check, check. I'm like the poster child for PMLE.
PMLE is caused by UV rays, so the only way to prevent it is stay out of the sun. Broad-spectrum sunscreen (I'm talking like UVA/UVB 60+...and yes, they make it that high), a floppy hat (which I bought just for this trip), clothing, and the shade is the only way to stop it. It's recommended to stay out of the sun between 10 am and 4 pm, when UV rays are the most intense. PMLE is possibly hereditary, though no one knows why some people are more sensitive to UV rays than others. I can certainly say neither my mother nor my sister seem to have this problem...ugh. One thing that can help is phototherapy. Instead of just blasting my skin with UV rays when we go on vacation I could start tanning to decrease sensitivity and prevent flare-ups. But tanning costs money, takes time (the nearest tanning bed is 15 minutes away from where I live!) and gives you cancer. I'll keep my sun disease, thank you very much.
Pretty much the only thing you can do once it starts is wait for it to go away. I usually bring Benedryl with me (antihistamines can help bring down the rash) and cortisone creams for the itching can also be applied. I don't generally do that; if you've ever had to put cortisone cream on a nasty, bumpy, hot rash, you'd understand the disgustingness of it. Being in the A/C helps me, personally, so I usually crank it up at nights. I actually sleep okay with PMLE, what with the Benedryl knocking me out and the nice cool room. It's typically a little better in the mornings, but gets worse as I'm out in the sun during the day. My PMLE clears up within about 2 days of not being in the sun, but for some people it can take up to a week. And I thought I had it bad.