How do I treat an absess until I can get the vet to come out?

Soak animalintex or human wound dressing (lint) in warm saline solution and bandage on - the hot poultice helps draw the infection out. If you don't have the lint, use a bag of warm bran or oats. You can fold the poultice material in any clean material - a new j-cloth or clean dish towel. Test the temp of the poultice - if you find it so warm so will your horse.