Nodule Formation Associated With Botulinum Neurotoxin Type A Injections: Potential Triggers in 23 Patients

The formation of nodules at injection sites following botulinum neurotoxin type A (BoNTA) treatment has recently been reported. This complication can cause significant distress for patients, primarily due to the uncertainty surrounding its etiology and progression, as well as the lack of established management strategies. However, this complication has not been thoroughly studied. In this retrospective series, we detailed 23 female participants aged between 35 and 65 years who developed nodules at the injection sites after receiving BoNTA. All participants experienced the formation of nodules within 24 hours of the procedure. We investigated potential triggers for this reaction, including infection, vaccination, and the diluent composition used in the injections. Notably, all patients had received the COVID-19 vaccine and booster before their BoNTA treatment. Management strategies implemented included oral antibiotics, oral serratiopeptidase, topical or systemic steroids, and oral antihistamines. The resolution times for the nodules after treatment ranged from a few days to 1 month. This complication may indicate an immediate hypersensitivity reaction. The potential association between this complication and the COVID-19 vaccination warrants further investigation. It is important to counsel patients about the benign nature of these complications.