(From Clare's article archives, Circa 2010-2015)
Sunburn can definitely be a very real problem, especially with horses that have white pigment on their noses and around their eyes, as seen with this Paint horse:
The pink skin is sensitive and prone to sunburn, as seen on this Palomino's sweet blaze:
Applying a sunscreen lotion or ointment works great.
There are lots of Sunscreen products made specifically for horses.
You should be able to find them quite easily at a tack or feed store, or on the Internet.
Also, products for Sunburn, if the sun has already done its damage. ***Helpful Hint***
Sunscreen or sunburn products made for humans work great as well!
I like to choose products for children or infants, as they focus on being especially
soothing for sensitive skin, and non irritating to the wearer.
Please be certain to pick a product that is made for the face!
Around the eyes and the nose for horse's requires the same care as for humans!
You should be able to pick something up very inexpensively at the Dollar Store,
or any Drug store or Market.