title: In vitro evaluation of concurrent use of commercially available insect repellent and sunscreen preparations.
abstract: BACKGROUND
  Insect repellents and sunscreens are over-the-counter products extensively used by the general public. Concurrent application of these products has become widespread in many regions across North America, because of concerns about West Nile virus and skin cancers.
  
  
  OBJECTIVE
  We investigated whether formulation type, application amount, and sequence would affect the percutaneous absorption profiles of the active repellent and sunscreen ingredients.
  
  
  METHODS
  In vitro percutaneous permeation of the repellent N,N-diethyl-m-toluamide (DEET) and the sunscreen oxybenzone from concurrent application of five commercially available products (A, repellent spray; B, repellent lotion; C, sunscreen lotion; D and E, combined repellent/sunscreen lotions) was measured and compared using Franz-style diffusion cells with piglet skin at 37 degrees C.
  
  
  RESULTS
  Penetration of DEET in A and B increased by 1640% and 282%, respectively, when C was applied concurrently. Penetration of DEET in D and E was 53% and 79% higher than that in B. Permeation of DEET from A + C (2:1) and A + C (1: 2) increased by 530% and 278%, respectively. Permeation of oxybenzone was 189% and 280% higher in A + C and B + C than in C. Permeation of oxybenzone in D and E was also 221% and 296% higher than that in C. Permeation of oxybenzone was 196% greater when A was applied on top of C than when C was applied on top of A, while oxybenzone in A + C (1:2) permeated 171% more than that in A + C (2:1).
  
  
  CONCLUSIONS
  Concurrent application of commercially available repellent and sunscreen products resulted in significant synergistic percutaneous permeation of the repellent DEET and the sunscreen oxybenzone in vitro. The percutaneous penetration profiles were dependent upon the type of formulation, application sequence and application proportion.
authors.affiliation: Faculty of Pharmacy, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada. xgu@cc.umanitoba.ca
authors.forename: X
authors.initials: X
authors.lastname: Gu
authors.forename: T
authors.initials: T
authors.lastname: Wang
authors.forename: D M
authors.initials: DM
authors.lastname: Collins
authors.forename: S
authors.initials: S
authors.lastname: Kasichayanula
authors.forename: F J
authors.initials: FJ
authors.lastname: Burczynski
mesh_terms: D000287:Administration, Topical; D000818:Animals; D001577:Benzophenones / Q000008:administration & dosage* / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid; D003671:DEET / Q000008:administration & dosage* / Q000493:pharmacokinetics; D004334:Drug Administration Schedule; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D007302:Insect Repellents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D023421:Models, Animal; D004366:Nonprescription Drugs; D012869:Skin Absorption / Q000187:drug effects*; D013473:Sunscreening Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics; D013552:Swine
chemical_list: D001577:Benzophenones; D007302:Insect Repellents; D004366:Nonprescription Drugs; D013473:Sunscreening Agents; D003671:DEET; C005290:oxybenzone