title: Cross-sensitization profiles of edible nuts in a birch-endemic area.
abstract: BACKGROUND
  Sensitization to birch pollen causes cross-sensitization to nuts, but rarely leads to clinical nut allergy. The aim was to study sensitizations to nuts in individuals sensitized to birch pollen and examine cross-reactivities between birch and nut species.
  
  
  METHODS
  All subjects with skin prick tests (SPTs) for birch pollen conducted during 1997-2013 in the Skin and Allergy Hospital in Helsinki (n = 114 572) and their available SPTs for nuts (n = 50 604) were included. Nut sensitizations were analyzed both with and without cosensitization to birch and stratified into age-categories. Cross-reactivities were analyzed with hierarchical clustering. One group of 1589 patients was surveyed for symptoms. Data were gathered also from Lapland to examine sensitizations in an area with less birch-pollen exposure.
  
  
  RESULTS
  Of subjects with birch sensitization, 84% were cosensitized to hazelnut, 71% to almond, and 60% to peanut. In a subgroup without birch sensitization, young children (<5 years) were most commonly nut-sensitized (8-40%); and this prevalence decreased in adolescents and further in adults (4-12%). Cashew and pistachio (ρ = 0.66; P < 0.001) and pecan and walnut (ρ = 0.65; P < 0.001) correlated the strongest. The majority of nut-sensitized patients (71% hazelnut, 83% almond, 73% peanut) reported no or mild symptoms. Cosensitizations between nuts and birch were similar in Lapland with its lower birch-pollen exposure.
  
  
  CONCLUSIONS
  Birch-sensitized individuals are frequently cosensitized to hazelnut, almond, and peanut. Among the birch-negatives, prevalences of nut sensitizations decrease from early childhood to adolescence. Cashew and pistachio, and pecan and walnut cross-react the most.
authors.affiliation: Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: R
authors.identifier: http://orcid.org/0000-0001-5708-2770
authors.initials: R
authors.lastname: Uotila
authors.affiliation: Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: A K
authors.initials: AK
authors.lastname: Kukkonen
authors.affiliation: Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: A S
authors.initials: AS
authors.lastname: Pelkonen
authors.affiliation: Skin and Allergy Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland.
authors.forename: M J
authors.initials: MJ
authors.lastname: Mäkelä
mesh_terms: D000367:Age Factors; D000485:Allergens / Q000276:immunology*; D052179:Antigens, Plant / Q000276:immunology; D029662:Betula / Q000009:adverse effects*; D016000:Cluster Analysis; D031211:Corylus / Q000009:adverse effects; D003429:Cross Reactions / Q000276:immunology*; D006801:Humans; D007114:Immunization; D021184:Nut Hypersensitivity / Q000175:diagnosis / Q000453:epidemiology* / Q000276:immunology*; D009754:Nuts / Q000009:adverse effects*; D015995:Prevalence; D012882:Skin Tests
chemical_list: D000485:Allergens; D052179:Antigens, Plant
keywords: birch pollen; birch sensitization; cross-reactivity; nut hypersensitivity; oral allergy syndrome