In my family if we have a boil, or acne that won't head up, we simply apply a slice of onion and hold it in place with masking tape for a half hour, then remove. This will bring many infections to a head. After draining them we again apply the onion for another half hour to make sure it's drawn everything out. A friend of mine had a rabbit with a puss-filled sore on the top of its head and it was not responding to the vet's medication. She was afraid she would lose her rabbit. I told her about this and the next day she called to say, "It worked! You saved my rabbit's life!"