to prevent, i'd use an equifit bellyband. to treat, i'd use corona cream. if it looks dirty, clean it out w betadine, iodine, or hydrogen peroxide. if the rub looks deep, this could be a result of you using the spurs incorrectly, so if you are at all unsure, ask your trainer.
Don't constantly use spurs and when u use them don't always be using them on your horses side
Vetricyn will help clear up the spot!
Buy him a thin belly band! Not one that is too thick or else he'll boil this summer
Belly band and leave a spur patch when clipping
There is rubber balls u can put on ur Spurs to help with that. I had a horse who I had trouble with rubs of my spurs.
You can get a saddle pad on smartpak that has a longer Velcro flap that goes down that far
You can get spur guards to help with spur rubs if your horse is naturally sensitive! I know some people will say you're using your spurs to hard but some horses just have extremely sensitive skin!