title: Effect of topical clay application on the synthesis of collagen in skin: an experimental study.
abstract: BACKGROUND
  Clay is often used in cosmetic treatments, although little is known about its action.
  
  
  OBJECTIVE
  To evaluate the effect of topical clay application on the histoarchitecture of collagen fibres in rat skin.
  
  
  METHODS
  Animals received a daily application of clay and retinoic acid (RA) 0.025% to the dorsal skin over 7 and 14 days, under vaporization at 37 °C for 40 min. Control skin was not vaporized. Samples from each region were excised, and stained with picrosirius red for collagen evaluation.
  
  
  RESULTS
  Seven days after clay treatment, an increase in the number of collagen fibres was observed in treated skin compared with control skin (51.74 ± 1.28 vs. 43.39 ± 1.79%, respectively, P < 0.01), whereas RA did not alter the collagen level (45.66 ± 1.10%). Clay application over 14 days did not induce a further increase in skin collagen, whereas treatment with RA did (58.07 ± 1.59%; P = 0.001 vs. control).
  
  
  CONCLUSIONS
  Clay application promotes an increase in the number of collagen fibres, which may account for its beneficial effects.
authors.affiliation: Department of Physiology, ABC Faculty of Medicine, University of São Paulo, São Paulo, Brazil.
authors.forename: D M Z
authors.initials: DM
authors.lastname: Valenti
authors.forename: J
authors.initials: J
authors.lastname: Silva
authors.forename: W R
authors.initials: WR
authors.lastname: Teodoro
authors.forename: A P
authors.initials: AP
authors.lastname: Velosa
authors.forename: S B V
authors.initials: SB
authors.lastname: Mello
mesh_terms: D000287:Administration, Topical; D000538:Aluminum Silicates / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000077215:Clay; D003094:Collagen / Q000187:drug effects*; D003358:Cosmetics / Q000008:administration & dosage / Q000494:pharmacology*; D007641:Keratolytic Agents / Q000494:pharmacology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000187:drug effects*; D014212:Tretinoin / Q000494:pharmacology
chemical_list: D000538:Aluminum Silicates; D003358:Cosmetics; D007641:Keratolytic Agents; D014212:Tretinoin; D003094:Collagen; D000077215:Clay