Has anyone had a dog suffer from this?

Mia has a couple of infected blister-ish type spots appear on her muzzle and so I took her to the vets last night.  She has a 5 day course of antibiotics.   Just wondered if anyone else had a dog suffer from this, any suggested causes and will the "inflammed areas" go back down so she has a normal muzzle again? 

One area burst this evening, so I squeezed it and it discharged watery type blood.  A smaller spot burst at the beginning of the week and that had pus in it. 

Hope everyone has had their tea?  

Christine