Dedicated runners spend a lot of time outdoors. Even a casual runner will tend to be out in the sunshine for hours a week. And it's really easy to forget that your skin is exposed to the elements the whole time you are out running.
Depending on weather conditions that can be everything from bitingly cold wind blasting your face - drying out skin and damaging it (every had wind burnt lips?). Right through to the more obvious sunburn. Our skins can generally only take a small amount of sunshine at a time without burning. Although that varies greatly by where you live and your skin type of course. Those with lighter or very pale skins will already be starting to burn by the time you've finished your stretches and warm-ups. And if you happen to be using any kind of skin whitening cream (such as this), then it's even more important. Yes, men do use these whitening products too, so this applies to everyone.
So if you're out running in the sun, do make sure you cover up wherever it's comfortable to do so. Personally I'm happy running in a cap, but some don't like to, in which case use plenty of sunscreen on your head (don't forget ears and neck). And don't neglect your arms, legs and hands. Some areas of skin aren't as sensitive so don't burn as readily, but if you're running for 4 or 5 hours, they will eventually burn too. If you do get burnt, despite your best efforts, then don't just 'tough it out' because you do need to treat sunburn.
But also protect your lips and your face too. You can get lip balms with sunscreens in them. And to protect your face form wind damage just apply a heavy layer of moisturiser before you go out - and yes, guys can do this too. You can buy fancy creams if you like or simply use something like olive oil - very effective and readily available.