Serum Sickness After Cosmetic Botulinum Toxin Type A Injections.

Botulinum toxin type A (BoNT-A) is widely used in therapeutic and cosmetic settings for neuromuscular and aesthetic indications. Although generally well tolerated, reports of hypersensitivity reactions-ranging from localized erythema to systemic immune syndromes-underscore its immunological complexity. This case report and literature review demonstrates a novel case of serum sickness following cosmetic Botox® (onabotulinumtoxin-A, Allergan Aesthetics, an AbbVie company, Irvine, CA) administration, categorizes hypersensitivity reactions according to the Gell and Coombs classification (Types I-IV), explores the role of complexing proteins and formulation excipients, and highlights emerging clinical concerns. This will underscore the need for greater vigilance in identifying systemic immune responses to BoNT-A especially within the cosmetic medicine industry. Level of Evidence: 5 (Therapeutic).