Is it starting?

The last and only time I ever had hell's itch was my senior year of high school. I was on a senior trip and got the privilege of acting like a crazy person in front of all my classmates. I'm now burnt again, and I'm scared. So I've got 2 questions. If I've had this before, am I likely to get it again? And how does it start?

I'm feeling a bit itchy but nothing severe, I'm on about hours 36 since I was in the sun. What signs should I look for, and what premptive actions can I take to save myself?