title: Facial blanching due to neurotoxins: proposed mechanisms.
abstract: BACKGROUND
  The effect of perceived facial blanching with neurotoxin therapy has been described in the literature and has been used to treat the undesirable facial flushing of Frey's syndrome. Patients rarely report it as a complication after cosmetic injection, but it can be distressing.
  
  
  OBJECTIVE
  To elucidate the proposed mechanism(s) of this unusual vasculocutaneous phenomenon, we reviewed normal physiologic responses to heat stress and the role of cholinergic neurotransmission in modulating cutaneous vascular tone in the context of the literature.
  
  
  METHODS
  We report a case of a 32-year-old woman who complained of white patches on her forehead at sites of abobotulinumtoxinA injections administered 2 weeks before presentation.
  
  
  RESULTS
  Acetylcholine is a primary mediator of cutaneous vasodilatation; certain co-transmitters modulate its effect. Chemical denervation by botulinum toxin (BoNT) appears to interfere with these normal signaling pathways and can provide symptomatic relief to patients with undesirable facial flushing. Conversely, it may create an unwanted cosmetic effect in patients who desire isolated muscle paresis.
  
  
  CONCLUSIONS
  Skin sites injected with BoNT type A may not experience the expected decrease in cutaneous vessel tone associated with higher body temperature. The exact mechanism remains unclear.
authors.affiliation: Department of Ophthalmology, Health Sciences Center, Louisiana State University, New Orleans, Louisiana, USA.
authors.forename: Tanya T
authors.initials: TT
authors.lastname: Khan
authors.forename: Kathleen
authors.initials: K
authors.lastname: Herne
authors.forename: Steven H
authors.initials: SH
authors.lastname: Dayan
authors.forename: Julie A
authors.initials: JA
authors.lastname: Woodward
mesh_terms: D000328:Adult; D019274:Botulinum Toxins, Type A / Q000009:adverse effects / Q000378:metabolism / Q000494:pharmacology*; D004890:Erythema / Q000188:drug therapy; D005145:Face / Q000098:blood supply; D005260:Female; D006801:Humans; D009498:Neurotoxins / Q000009:adverse effects / Q000378:metabolism / Q000494:pharmacology*; D010167:Pallor / Q000139:chemically induced*; D015398:Signal Transduction / Q000187:drug effects; D012867:Skin / Q000098:blood supply; D013547:Sweating, Gustatory / Q000188:drug therapy; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D009498:Neurotoxins; D019274:Botulinum Toxins, Type A; C542869:abobotulinumtoxinA