Otherwise you could turn him out at night, avoid the sun and many bugs. Buy cheap high number sunscreen and apply daily. Buy plain zinc oxide, the protective part in many sunscreens, and apply the zinc oxide as sunscreen.
When mine gets sunburnt I take a little dab of suntan lotion, and a little dab of fly spray. More suntan lotion than the spray, mix them together in the palm of my hand and then rub it on her nose. It works really well! I apply daily until healed!
I got a different type of aloe vera gel today. Max REALLY liked it. He was all fidgety before and as I was applying, but after a few seconds, he just stood there with his head down.
Did Max have this sunburn when you got him back last week, or is it new or worsening?
Because, very often it is caused (or anyhow greatly amplified) by plants in the pasture (or more rarely in the hay). St Johns Wort is a very common offender, but many others can do it as well, including large amounts of many legumes (clover, alfalfa, etc).
Google "horse photosensitization plants" or something like that, then go walk his pasture.
In the meantime a long-nose fly mask and/or white zinc oxide cream will also help.
While Aloe is a great healer, I don't think it is sun protective. Might even worsen a burn! Kind of like vasaline, just intensifies the burning action. I sunburned my horse's face with the vasaline on for shine at a horse show years ago. Forgot to rub it off after Showmanship. She actually peeled and was a dark skinned horse!!
So maybe a diaper cream with medication and zinc oxide in the contents as a healing item on the burns. You HAVE to read labels to know what you are getting in meds.
I would not want cheap or expensive aloe on skin exposed to sun where it could make a burn worse. Maybe aloe mixed with other stuff for sun protection, but not plain aloe on a burn the sun can shine on. Reminds me of the old days when kids rubbed cooking oil on skin to get tanned. Did DARKEN you up after you burned!!
patandchickens, yes, he had a sunburn when I got him back, but it's definitely gotten worse. It was a light yesterday morning and turned red and was cracking throughout the day.
greathors, I used the aloe vera as a cooling agent and to apply moisture in his poor nose. 10 minutes later, I applied a 50 SPF sunscreen to help protect his nose from further sun.
It's what I used to do when I worked at the chicken houses. Apply the aloe vera to cool the burn and soothe, then apply sunscreen to protect.
The vet told me to use a cheap diaper cream on my mare's nose to let the sunbrun heal. She had scraped the hair off her nose and the skin had bruned from the sun. I put it on her nose for 3 days and it worked great.