Olfactory function in patients with postinfectious and posttraumatic smell disorders before and after treatment with vitamin A: a double-blind, placebo-controlled, randomized clinical trial

Laryngoscope. 2012 Sep;122(9):1906-9. doi: 10.1002/lary.23405. Epub 2012 Jul 2.


Objectives/hypothesis: In this study we investigated the effectiveness of vitamin A in postinfectious and posttraumatic smell disorders. A possible effect of vitamin A is likely due to the stimulation of regeneration and repair of the peripheral olfactory system.

Study design: Double-blind, randomized, placebo-controlled clinical trial.

Methods: A total of 52 patients (age range, 20-70 years; mean age, 52 years) participated, 26 of whom received placebo (7 male, 19 female) and another 26 verum (8 male, 18 female). A standardized history was obtained in each patient. Olfactory function was measured by means of the Sniffin' Sticks test kit, a validated technique to investigate odor thresholds, odor discrimination, and odor identification. Vitamin A was prescribed at a dose of 10,000 IU per day for 3 months. Follow-up testing was performed on average 5 months after the first investigation.

Results: Forty-four percent of all patients reported recovery of their sense of smell; 29% of the participants exhibited significant improvement in measured olfactory function. However, there was no significant difference between the outcome of patients receiving verum or placebo.

Conclusions: The systemic application of vitamin A at a dose of 10,000 IU per day for 3 months does not appear to be useful in the treatment of postinfectious or posttraumatic olfactory loss.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Administration, Oral
  • Adult
  • Aged
  • Analysis of Variance
  • Dose-Response Relationship, Drug
  • Double-Blind Method
  • Drug Administration Schedule
  • Female
  • Follow-Up Studies
  • Humans
  • Male
  • Middle Aged
  • Nose / injuries*
  • Olfaction Disorders / drug therapy*
  • Olfaction Disorders / etiology
  • Olfaction Disorders / physiopathology
  • Olfactory Nerve / physiopathology*
  • Reference Values
  • Rhinitis / complications
  • Rhinitis / diagnosis
  • Severity of Illness Index
  • Smell / drug effects*
  • Treatment Outcome
  • Vitamin A / therapeutic use*
  • Wounds and Injuries / complications
  • Young Adult


  • Vitamin A