Can only one sunburn cause skin cancer? How much is the risk?

Hi, Yesterday (July 20th) I got a very bad sunburn on my back and hands. I was snorkeling at Hawaiian beaches for almost 3 or a little more hours from 11:00 to 14:30 at noon. The weather was somewhat cloudy. so I was deceived and didn't use any sunscreen. Now, my skin has become so irritated (specially on the shoulders, though there is no sign of blistering yet). despite the deep irritation and pain it seems to be a first degree burn. Should I worry about developing any skin cancer in the future? (considering the facts that I'm now 25 years old with a white Caucasian skin and I have always protected my skin against sun light and this was in fact the first time that I was exposed to very high exposure without any protection. I have also lots of moles on my skin, a couple of them on my back, one of them ~5mm diameter, but regular) How far does it take to blister if it's gonna happen? TNX

Please don't worry about it but try to avoid this happening in the future. Myself and many people I know, (some of us with lots of moles and on our backs) have caught bad sunburn on our backs in similar circumstances to you over the years. Watch out for overcast skies and cool breezes from the sea. Use high factor sunscreen. If you want to sit in the sun after being burnt the very highest factor should help with discomfort and also keep yourself covered.

Try not to worry about this. A bad sunburn (i.e. blistering) in your childhood can increase the risk of developing skin cancer latter in life. However, at your age, the skin is much more resilient. Blisters tend to show up pretty quickly (within a day), so the burn may not be as bad as it looks or feels. You've been very good about protecting your skin in the past, so this one incident is not likely to increase your chances of developing anything. Hope that burn doesn't hurt too bad. Aloe vera works wonders!