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Humidified air is not indicated for mild to moderate croup

Three Part Question

In [children with mild to moderate croup] is [humidifed air better than room air] at [improving clinical symptoms and signs]?

Clinical Scenario

You have seen a 2 year old boy with croup, using parameters based on his clinical features you work out his Westely score is less than 7. He can be discharged with oral steroids. Do you advise his parents to treat with humidified air?

Search Strategy

Medline 1966-present using the Ovid interface.
([Child OR Children].mp AND [croup OR viral croup].mp AND OR ([Child OR Children].mp AND [croup OR viral croup].mp AND [humidity/ OR] LIMIT to human AND English language AND abstracts.

Search Outcome

20 articles were found using Medline, of which 3 were relevant to the question. One further study was found using a reference search.

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Neto et al,
71 patients, aged between 12 and 36 months. Patients presenting to the ED with Croup and a Westely Croup score of 2-7. 35 patients were randomized to mist and 36 received no mist therapyRandomized, controlled, single blind studyChange from baseline Westerly score was measured at 30, 60, 90 and 120 minsNo significant difference in the two groups' Westerly Score was found (p=0.39)Single blind study
Bourchier D et al,
New Zealand
46 patients were recruited between 3 and 6 years old. Patients had a modified Taussig score of 1-8. 22 patients were treated and 26 were not (see study weaknesses)Randomized controlled trialWestley score up to 12hrs from presentationNo therapeutic benefit was found for the treatment group (no significant difference using Mann-Whitney U test at 0, 6 and 12 hours). Baseline scores were 3.0 (s.d 0.87) and 3.75 (s.d. 0.83) in the control and treatment groups respectively. At 12 hrs they were 2.0 (s.d. 1.32) and 2.63 (s.d. 1.49) respectivelySmall number of patients No evidence of blinding
Jamshidi et el,
46 patients were recruited between 3 and 6 years old. Patients had a modified Taussig score of 1-8. 22 patients were treated and 26 were not (see study weaknesses)Randomized, controlled, single blind studyChange in croup score was measured at 20 minsBaseline croup scores were not significantly different (3.5 +/- 1.8 vs 3.5 +/- 1.9, p=0.87), however after treatment the scores improved (2.2 +/- 1.6, p=<0.05). There was no significant change in the control group (3.5 +/- 1.9, p=1)46 patients were recruited yet 22 treated and 26 controls Unexplained statistical power
Lenny et al,
5 control patients received nebulized water. Aged 4 – 18 monthsUncontrolled with respect to nebulized water. No randomizationPulse rate, and blood pressure (Respiratory resistance was also measured but not relevant to this review)No clinical (or objective) improvement after nebulized waterThe nebulized water group was the control group, this study primarily focused on the effect of nebulized an alpha-adrenergic stimulant Very small numbers No stated randomisation


A number of different methods for delivering humidified air to children with croup have been devised. Parents have in the past spent great time and effort giving these treatments. This review aims to look at whether this treatment is warranted. Although 4 studies were found, none were double-blind Randomized controlled trials. 2 were single-blind RCT's, but numbers were low in all of the studies. 3 of the studies concluded that there was no significant benefit from humidified air and one found there was a significant improvement in croup scores. On balance, the evidence suggests humidified air is not useful in improving clinical features.

Clinical Bottom Line

The balance of evidence suggests that humidified air is unlikely to be a useful treatment in mild to moderate croup.


  1. Neto GM, Kentab O, Klassen TP et al. A randomized controlled trial of mist in the acute treatment of moderate croup Academic Emergency Medicine 2002;9(9):873-9.
  2. Bourchier D, Dawson KP, Fergusson DM. Humidification in viral croup: a controlled trial. Australian Paediatric Journal 1984;20(4):289-91.
  3. PB Jamshidi, JS Kemp, JR Peter, et al. The Effect of Humidified Air in Mild to Moderate Croup Acad Emerg Med 2001;8:417.
  4. Lenney W, Milner AD. Treatment of acute viral croup. Archives of Disease in Childhood 1978;53(9):704-6.