title: Allergenicity of casein containing chalk in milk allergic schoolchildren.
abstract: BACKGROUND
  Nondietary exposure to milk proteins may be a risk for children who do not outgrow milk allergy by school age.
  
  
  OBJECTIVE
  To study the allergenicity of casein containing chalk.
  
  
  METHODS
  A 6-year-old, milk allergic child developed asthma and rhinoconjunctivitis while in school. The suspected cause was dust-free chalk containing casein. To study the relationship of dust-free chalk containing casein with asthma and rhinoconjunctivitis, 13 additional milk allergic patients were studied: 3 school-aged children, 8 preschool-aged infants, and 2 children with outgrown milk allergy. Skin tests and/or specific IgE with chalk and casein were performed. A chalk use test was performed in older children. Milk allergens contained in chalk were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblot, and IgE inhibition experiments.
  
  
  RESULTS
  All school-aged, milk allergic children were exposed to chalk and reported symptoms attributed to chalk exposure. The skin test result to chalk was positive in 5 of 12 cases, and the specific IgE test result was positive in all 12 study participants in which it was performed. Casein strongly inhibited the binding of IgE to chalk. Chalk sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed proteins with molecular weight similar to caseins. Immunoblot demonstrated strong binding of IgE to chalk in a blurred pattern and a band at 30 kDa, inhibited by casein. The chalk challenge test result was positive in 2 school-age children who had a positive skin test result to chalk. Their symptoms improved after avoidance of chalk in the school. In 2 other cases in which the challenge test result was negative, chalk was reintroduced without problems.
  
  
  CONCLUSIONS
  Inhalation of chalk dust containing casein can induce asthma symptoms in milk allergic patients. Hidden and nondietary sources of exposure should always be considered in food allergic patients.
authors.affiliation: Sección de Alergia, Hospital Marina Baixa, Villajoyosa, Alicante, Spain. chernandol@coma.es
authors.forename: Carlos H
authors.initials: CH
authors.lastname: Larramendi
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Marco
authors.forename: Mónica
authors.initials: M
authors.lastname: Llombart
authors.forename: Ana
authors.initials: A
authors.lastname: de la Vega
authors.forename: Eusebi
authors.initials: E
authors.lastname: Chiner
authors.forename: José Luis
authors.initials: JL
authors.lastname: García-Abujeta
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Sempere
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry / Q000276:immunology*; D002364:Caseins / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D004391:Dust; D005260:Female; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology; D007223:Infant; D008297:Male; D016269:Milk Hypersensitivity / Q000276:immunology* / Q000503:physiopathology; D012882:Skin Tests; D013147:Spirometry
chemical_list: D002364:Caseins; D004391:Dust; D007073:Immunoglobulin E; D002119:Calcium Carbonate