title: Topically applied ZnO nanoparticles suppress allergen induced skin inflammation but induce vigorous IgE production in the atopic dermatitis mouse model.
abstract: BACKGROUND
  Metal oxide nanoparticles such as ZnO are used in sunscreens as they improve their optical properties against the UV-light that causes dermal damage and skin cancer. However, the hazardous properties of the particles used as UV-filters in the sunscreens and applied to the skin have remained uncharacterized.
  
  
  METHODS
  Here we investigated whether different sized ZnO particles would be able to penetrate injured skin and injured allergic skin in the mouse atopic dermatitis model after repeated topical application of ZnO particles. Nano-sized ZnO (nZnO) and bulk-sized ZnO (bZnO) were applied to mechanically damaged mouse skin with or without allergen/superantigen sensitization. Allergen/superantigen sensitization evokes local inflammation and allergy in the skin and is used as a disease model of atopic dermatitis (AD).
  
  
  RESULTS
  Our results demonstrate that only nZnO is able to reach into the deep layers of the allergic skin whereas bZnO stays in the upper layers of both damaged and allergic skin. In addition, both types of particles diminish the local skin inflammation induced in the mouse model of AD; however, nZnO has a higher potential to suppress the local effects. In addition, especially nZnO induces systemic production of IgE antibodies, evidence of allergy promoting adjuvant properties for topically applied nZnO.
  
  
  CONCLUSIONS
  These results provide new hazard characterization data about the metal oxide nanoparticles commonly used in cosmetic products and provide new insights into the dermal exposure and hazard assessment of these materials in injured skin.
authors.forename: Marit
authors.initials: M
authors.lastname: Ilves
authors.forename: Jaana
authors.initials: J
authors.lastname: Palomäki
authors.forename: Minnamari
authors.initials: M
authors.lastname: Vippola
authors.forename: Maili
authors.initials: M
authors.lastname: Lehto
authors.forename: Kai
authors.initials: K
authors.lastname: Savolainen
authors.forename: Terhi
authors.initials: T
authors.lastname: Savinko
authors.affiliation: Nanosafety Research Centre, Finnish Institute of Occupational Health, Helsinki 00250, Finland. harri.alenius@ttl.fi.
authors.forename: Harri
authors.initials: H
authors.lastname: Alenius
mesh_terms: D000279:Administration, Cutaneous; D000485:Allergens; D000818:Animals; D018926:Anti-Allergic Agents / Q000008:administration & dosage / Q000633:toxicity*; D015415:Biomarkers / Q000097:blood; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D003876:Dermatitis, Atopic / Q000097:blood / Q000139:chemically induced* / Q000235:genetics / Q000276:immunology / Q000517:prevention & control*; D004195:Disease Models, Animal; D015536:Down-Regulation; D004768:Enterotoxins; D005260:Female; D007073:Immunoglobulin E / Q000097:blood*; D008264:Macrophages / Q000187:drug effects / Q000276:immunology; D053768:Metal Nanoparticles / Q000008:administration & dosage / Q000633:toxicity*; D008807:Mice, Inbred BALB C; D010047:Ovalbumin; D012333:RNA, Messenger / Q000378:metabolism; D018570:Risk Assessment; D012867:Skin / Q000187:drug effects* / Q000276:immunology / Q000293:injuries; D013473:Sunscreening Agents / Q000008:administration & dosage / Q000633:toxicity; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D015034:Zinc Oxide / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D000485:Allergens; D018926:Anti-Allergic Agents; D015415:Biomarkers; D016207:Cytokines; D004768:Enterotoxins; D012333:RNA, Messenger; D013473:Sunscreening Agents; D007073:Immunoglobulin E; C031818:enterotoxin B, staphylococcal; D010047:Ovalbumin; D015034:Zinc Oxide