Hypersensitivity Reactions Following Onabotulinum Toxin A Touch-up Injection Possibly Associated with Covid-19 Infection.

As one of the most common cosmetic procedures, botulinum toxin A (BTX-A) injections are basically safe. The typical allergic reactions include erythema, edema, pruritus, and wheal, which generally occur at the initial injection. Herein, we reported two cases of hypersensitivity reactions following cosmetic BTX-A touch-up injection. Type I allergic reactions provoked by re-exposure to the excipients such as gelatin may play a role in the event. In addition, this condition may be associated with the preceding Covid-19 infection, even with complete symptoms remission and negative tests results. Noteworthily, one case developed anaphylactic symptoms resembling purpuric drug eruption (PDE). These cases may serve as a significant complement to the botulinum toxin treatment safety profiles. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .