Atypical Hypersensitivity Reaction to Botulinum Toxin Injection: A Case Report

Case Diagnosis: Allergic Reaction to Botulinum Toxin Injection

Case Description or Program Description: 29-year-old female with a history of chronic migraines, cervicogenic headaches, and intermittent asthma presented for administration of botulinum toxin injections (reconstituted with 0.9% normal saline to a concentration of 100U/0.1cc) for treatment of cervicogenic headaches and cervical dystonia. She received injections to the frontalis, procerus, left temporalis, obliquus capitis inferior, left sternocleidomastoid, trapezius, and left levator scapulae. She reported immediate flushing, lightheadedness and nausea after the first injection, which slowly worsened with each subsequent injection. Upon attempted injection of the left levator scapulae, the patient requested to cease receiving further injections. She then experienced vomiting.

Setting: Outpatient Physiatry Clinic

Assessment/Results: Upon returning home, the patient reported continued symptoms of nausea and vomiting throughout the day despite treatment with sublingual Ondansetron HCl. After 12 hours of ongoing symptoms, the patient reported taking Cetirizine HCl 10mg and Diphenhydramine HCl 25mg, which improved her symptoms. Her symptoms continued through the next ten days, improving intermittently with alternating the above antihistamine administration. The patient reported complete resolution of her symptoms after 10 days.

Discussion (relevance): This is the first reported case, to our knowledge, of type I hypersensitivity reaction following botulinum toxin injections given at what is commonly considered to be a standard dose for adults with cervicogenic headache and cervical dystonia. In this case improvement of symptoms with antihistamine administration points to likely abnormal allergic response to botulinum toxin type A.

Conclusions: Treatment with botulinum toxin is widely viewed as safe, effective and largely devoid of serious side effects. This case describes an extremely rare circumstance of type I hypersensitivity reaction following botulinum toxin type A injection. Consideration of prophylactic administration of antihistamines or other immunosuppressive agents such as steroids may be helpful in preventing the incidence of future hypersensitivity reactions to botulinum A toxin.