Most people have indoor cats and don't really think about how the sun can affect their cat. I once had a pure white cat that was an indoor cat for the first few years of her life. That was when we lived in suburbia. When she was just over 5 years old she moved with us to our first country property. At first she was unsure of the place and tended to want to hide in the garage most of the time. Soon she loved to hang around outside the front door under several trees that lined the front of the house. As summer slowly approached we soon discovered that the tips of her ears were starting to look "crispy." She had developed severe sunburn.
Treating her ears was not a simple task of just putting sunscreen on her. I first had to treat the ears with something that would heal the wounds and that was not toxic to the cat and also find something she would not lick off. At the time I did not have a cat first aid book with any references in it to sunburn so I had to resort to reading all the labels at the stuff on sale at the local pet store – this was long before the internet had all of the information it has on it now. Nowadays you can not only get a book on first aid for cats but they come with DVD's, computer reference guides and videos too, like this one:
If I had only had something like that, I would have not been stuck reading labels. Anyway, I ended up using a product that is commonly used on horses to prevent sunburn, since white horses or the areas they have white fur, tend to burn too. The funny thing about the cat is that the tips of ears were the only part of her body to have sunburn, not even her pink nose was affected.