title: Contact Urticaria to Nickel: A Series of 11 Patients Who Were Prick Test Positive and Patch Test Negative to Nickel Sulfate 2.5% and 5.0.
abstract: BACKGROUND
  Nickel is the most common allergen found by patch testing; however, not all cases of nickel allergy are type 4 (delayed) allergies. Contact urticaria (CU) to nickel (immediate reaction) has been reported; however, few seem to evaluate it as per a recent published survey of American Contact Dermatitis Society members.
  
  
  OBJECTIVE
  The aim of the study was to present a series of patients who had clinical histories suggestive of nickel allergy and yet were patch test negative but prick test positive to nickel, thus demonstrating CU.
  
  
  METHODS
  We reviewed the charts of 11 patients who were patch test negative but prick test positive.
  
  
  RESULTS
  All 11 patients demonstrated evidence of CU by prick testing (or closed chamber test in 1). None were patch test positive to nickel 2.5% or 5.0%. Four patients' histories mentioned reactions to various jewelry/earrings within minutes, whereas 2 histories mentioned reacting within a few hours. These histories are consistent with CU. Others (except 1 patient) recalled reacting to jewelry/earrings but did not recall a time frame.
  
  
  CONCLUSIONS
  Our series suggests that CU to nickel may be far more common than anticipated and should be evaluated with prick testing when patients' history suggests nickel allergy and yet they are patch test negative.
authors.affiliation: From the Department of Dermatology, University of Utah School of Medicine, Salt Lake City.
authors.forename: Sandeep S
authors.initials: SS
authors.lastname: Saluja
authors.forename: Crystal L
authors.initials: CL
authors.lastname: Davis
authors.forename: Tracie A
authors.initials: TA
authors.lastname: Chong
authors.forename: Douglas L
authors.initials: DL
authors.lastname: Powell
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007428:Intradermal Tests / Q000379:methods; D007509:Irritants / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009532:Nickel / Q000009:adverse effects; D010328:Patch Tests / Q000379:methods; D014581:Urticaria / Q000139:chemically induced / Q000175:diagnosis*
chemical_list: D007509:Irritants; C029938:nickel sulfate; D009532:Nickel