buring forehead in sun

Hello,

I've had a problem in recent years that seems to be getting worse every year. This summer has been particularly bad. I don't burn easily, I could spend hours in the sun and not get burned, just lucky I guess. A few years ago though I don't remember exactly when it started but I felt like my forehead was burning. When I look in the mirror I see no redness or anything noticeable, it just burns. Now every summer I'm avoiding the sun for this reason. This summer it's like I can't even spend 5 minutes in the sun without having my forehead burn all day after. I do put on sunscreen too which doesn't seem to help. I'm usually walking around with my hand over my forehead to block any exposure. I would appreciate any medical advice on this situation.

Thanks.