<s>[INST] I was at dentist on Friday as I had a tooth abscess. I had some pain on biting but no swelling. The abscess showed up on an x ray. During root canal treatment on Friday my cheek started to swell up. The dentist said It has reacted and prescribed antibiotics. I ve to go back next week. What does he mean, it reacted? Am I allergic to something? [/INST] Thanks for using Health Care Magic.Read your query.Acute exacerbation of the chronic abscess usually causes the sudden increase in the swelling and pain when there is presence of abscess in the tooth. Since you are already on antibiotics and the root canal treatment is started, the swelling and pain will come down gradually.Do not discontinue the treatment .Do salt water gargling.Do not apply a hot bag externally.Hope this was helpful.Thanks and regards. </s>