My bitch once had mastitis which progressed to an 'open' wound (1cm) despite a course of antibiotics

I was terribly upset at it but the vet just laughed at me and said it wasn't as bad as it looked and gave her a different course of ab's and some painkillers. He recommended bathing 'downwards' with salt water to help it drain (I added tea tree oil as well ;) ) and within a week you couldn't even tell she'd had mastitis! all she had was a hairless patch

But this vet mostly treats farm animals so maybe the attitude is different ;)