dental abscess
"Had toothache for a week. Went to dentist. He cleaned out tooth and prepared for root canal.  Put temporary filling in. (2 month wait on NHS) Week later I have swelling on gum above tooth.  Another emergency appointment and given amoxcillin (penicillin) a week later my face on that side is swollen so much I look like I have a boiled sweet in there. Was given metronidazole.  By the morning of day 3 on them the dizziness nausea and fatigue had developed into severe tachycardia, depleted blood o2 near on respiratory failure."