I Saw A Doctor Yesterday For A Severe Blister On

i saw a doctor yesterday for a severe blister on bottom lip with extensive swelling (having just returned from mexico). I have never had cold sores. He prescribed valtrex. Today I sought a second opinion because the lip was 2x the size and the pain is nearly unbearable. Today I was given a Dx of cellulitis and put on 300mg of Clyndamycin 3x daily. My question is: when can I expect some relief in pain? It hurts much worse since this morning. I do think the swelling is going down somewhat.