title: Contact urticaria from carboxymethylcellulose in white chalk.
abstract: BACKGROUND
  Carboxymethylcellulose (CMC) is widely used in consumer goods, foods, and medicaments as a binder, emulsifier, and viscosity enhancer. Cases of immediate and delayed allergic reactions to this anionic cellulose polymer have been reported.
  
  
  OBJECTIVE
  To report a case of contact urticaria from CMC in chalk, with possible cross-reaction to methyl hydroxyethylcellulose (MHEC).
  
  
  METHODS
  Patch tests with readings at 48 and 96 hours were performed with the North American Contact Dermatitis Group standard series and benzisothiazolinone. Open and prick tests with readings after 30 minutes were performed with two brands of chalk as well as with various petrolatum and aqueous dilutions of CMC, MHEC, oleic acid, and calcium carbonate.
  
  
  RESULTS
  The patient developed strong urticarial reactions during open tests with both powdered chalks and had milder reactions to the open test with CMC 10% aqueous (aq) and to prick testing with CMC 0.1% aq. No reaction to MHEC or any of the other ingredients of the chalks was observed. No relevant delayed reaction was noted.
  
  
  CONCLUSIONS
  CMC can cause contact urticaria. It remains unclear why our patient reacted more strongly to the chalk than to CMC itself. We speculate that the abrasive nature of the chalk enhances the cutaneous penetration of CMC or that calcium carbonate, the main ingredient of the chalk, acts as an adjuvant. It is also possible that CMC and MHEC cross-react and that our negative results with MHEC may be due to improper testing technique or concentrations.
authors.affiliation: Division of Dermatology, McGill University Health Centre, Royal Victoria Hospital, Montréal and Greenfield Park, PQ, Canada.
authors.forename: Linda
authors.initials: L
authors.lastname: Moreau
authors.forename: Ghanima
authors.initials: G
authors.lastname: Alomer
authors.forename: Normand
authors.initials: N
authors.lastname: Dubé
authors.forename: Denis
authors.initials: D
authors.lastname: Sasseville
mesh_terms: D000293:Adolescent; D002119:Calcium Carbonate / Q000009:adverse effects*; D002266:Carboxymethylcellulose Sodium / Q000009:adverse effects*; D003429:Cross Reactions; D017449:Dermatitis, Allergic Contact / Q000175:diagnosis / Q000209:etiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000175:diagnosis / Q000209:etiology*; D010328:Patch Tests; D018570:Risk Assessment; D012720:Severity of Illness Index; D014581:Urticaria / Q000175:diagnosis / Q000209:etiology*
chemical_list: D002119:Calcium Carbonate; D002266:Carboxymethylcellulose Sodium