Benzocaine
"My dentist used Benzocaine gel/ointment to numb my gum prior to dental filling.   Within half an hour, my tongue, cheek,gum,lip,   complete side of face had swollen to painful gigantic proportions. I had to attend hospital as an emergency arranged by dentist , to see a max.facial consultant who had to prescribe an anti-histamine.   The swelling took well over a week to gradually subside to normal, but completely ruined my 65th family birthday party, a few days after, as I could barely speak and could have no photos taken !!!    I now check every medical spray or ointment/cream to ensure I am not using this chemical......"