 [ Symptoms ] how safe is botox cosmetic  a few months ago i had botox cosmetic injected into some facial lines about 10 days after i experienced hives or red welts on my torso it went away with benadryl but recurred every night for about a week each time it went away with benadryl after that i did not have any other problems have i now built up immunity towards the botox or is it possible to have a worse reaction in the future if i have further treatments [ Disease ] hi hives and red welts are a side effect of botox so you have had a warning that your allergic to them so after that would you think is wise to carry on good luck