Bronchiolitis — The Wheezing Infant and the Case for Doing Less

Lead

A baby a few months old breathing with a wheezing, whistling sound. For a parent hearing it for the first time, that sound is deeply alarming. This is the hallmark presentation of bronchiolitis — responsible for approximately 100,000 hospital admissions a year in the United States and the most common cause of hospitalization in the first 12 months of life [1], making it one of the most significant respiratory illnesses of infancy. What makes this disease unusual is the existence of a formal, evidence-based list of things not to do. Understanding the standard of care helps parents observe symptoms at home with more accuracy and make better decisions about when to seek help.

What Is Bronchiolitis?

Bronchiolitis is an inflammatory disease of the lower airways (bronchioles) affecting primarily children under two years of age. Inflammation causes the mucous membranes to swell, secretions to increase, and the already narrow airways to become prone to obstruction. This is what produces the characteristic wheeze and respiratory distress.

Respiratory syncytial virus (RSV) is the most common cause [2] — in one study cited by the AAP guideline, 76% of patients had RSV — but rhinovirus, human metapneumovirus (hMPV), and parainfluenza virus can also be responsible, and co-infections are common [1]. Seasonal patterns track RSV closely, peaking in autumn and winter.

Bronchiolitis is not asthma. Asthma is a chronic condition driven by bronchial hypersensitivity and characterized by recurrence; bronchiolitis is an acute illness that follows a viral infection. That said, infants who have had bronchiolitis are known to be at increased risk of recurrent wheezing [2], and in a Swedish prospective study, 43% of children hospitalized with RSV bronchiolitis in infancy had asthma or recurrent wheezing at age 13, versus 8% of controls [5] — though whether this is a causal relationship remains unclear.

The Course of Illness and Recognizing Severity

The illness begins with upper respiratory (cold-like) symptoms: runny nose, mild fever, cough. Over the next few days, wheeze and labored breathing become more prominent. The following observations are clinically useful for assessing whether hospitalization may be warranted:

• Sustained fall in oxygen saturation (SpO₂): the AAP allows clinicians to withhold supplemental oxygen when SpO₂ is above 90% [1], and the 2025 Australia/New Zealand guideline uses SpO₂ persistently below 90% (below 92% for infants under 6 weeks or with an underlying condition) as the threshold for oxygen [6]. Readings fluctuate, and in one randomized trial, simply displaying values 3 points higher than true cut emergency-department hospitalizations from 41% to 25% [3] — the number alone should not decide
• Tachypnea: when the respiratory rate exceeds 60 to 70 breaths per minute, feeding tends to become difficult [1]
• Retractions: visible inward movement of the skin below the neck, between the ribs, or above the collarbone during breathing
• Poor feeding: taking less than half of usual intake is a common marker of inadequate hydration [6]

Cyanosis — a blue or purple tint to the lips or fingernails — is a sign of high urgency.

The AAP Guideline's Case for Doing Less

The 2014 clinical practice guideline on bronchiolitis issued by the American Academy of Pediatrics (AAP) drew attention not for what it recommended, but for what it explicitly ruled out [1]. As of September 2026, the AAP has not issued a replacement bronchiolitis guideline, so the 2014 version remains current. The Australia/New Zealand guideline was updated in 2025; it keeps the same "do less" direction and goes further on some points [6].

The following interventions are not recommended for routine use in bronchiolitis, whether in inpatient or outpatient settings:

• Antibiotics: The cause is viral; there is no bacterial target, and antibiotics are not recommended unless a bacterial infection is confirmed or strongly suspected [1]
• Bronchodilators (β₂ agonists and others): The AAP recommends against both albuterol (salbutamol) and epinephrine [1]. A Cochrane review of epinephrine found short-term improvement in outpatients right after treatment, but no benefit for hospitalized infants [4]
• Systemic corticosteroids: Not recommended in any setting [1]. Combined with epinephrine, one trial showed a promising signal, but it has not been confirmed [4]; the 2025 Australia/New Zealand guideline leaves room for the combination only in severe cases requiring intensive care [6]
• Nebulized hypertonic saline: The AAP advises against it in the emergency department and allows it only for hospitalized infants (a weak recommendation) [1]. The 2025 Australia/New Zealand guideline recommends against routine use even in hospitalized infants outside of clinical trials [6]

This represents the outcome of an evidence-based reassessment: treatments that had been widely practiced simply failed to prove their effect.

What Supportive Care Actually Looks Like

The core of care is supporting breathing and hydration while the illness runs its course [2]:

• Nasal suctioning: Gently clearing secretions at the nostrils can temporarily relieve congestion and make feeding and breathing easier. Routine "deep" suctioning, however, has not been shown to help [1][6]
• Hydration: Keep feeding, offering smaller amounts more often. If intake falls below about half of normal, seek care
• Positioning: Holding the baby upright while awake may seem to ease breathing. For sleep, though, the rule remains flat on the back on a firm, non-inclined surface [7]

For hospitalized infants, supplemental oxygen is provided as needed. Tube feeding or intravenous fluids are added when oral intake is insufficient [1]. High-flow nasal cannula oxygen therapy is sometimes used when respiratory distress is marked.

Translating Evidence into Everyday Decisions

• If wheezing, poor feeding, and rapid breathing occur together, seek medical evaluation
• Knowing that antibiotics are not indicated for bronchiolitis helps a parent ask appropriate questions if they are prescribed
• Tracking the date symptoms began and how feeding quantities have changed provides the information a physician needs to assess hospitalization risk
• Humidifying the room is sometimes assumed to help, but evidence that it specifically affects bronchiolitis is limited

Summary

The great majority of bronchiolitis cases resolve on their own [2]. Supportive care is the mainstay of management; antibiotics, bronchodilators, and systemic corticosteroids are not recommended for routine use. What appears to be "doing nothing" is, in fact, the evidence-based choice. The decision to hospitalize should rest on respiratory rate, SpO₂, and feeding adequacy — not on the volume or character of the wheeze alone.

References

1. Ralston SL, Lieberthal AS, Meissner HC, et al.; American Academy of Pediatrics. Clinical practice guideline: the diagnosis, management, and prevention of bronchiolitis. Pediatrics. 2014;134(5):e1474–e1502. doi:10.1542/peds.2014-2742. PMID: 25349312.
2. Smyth RL, Openshaw PJ. Bronchiolitis. Lancet. 2006;368(9532):312–322. doi:10.1016/S0140-6736(06)69077-6. PMID: 16860701.
3. Schuh S, Freedman S, Coates A, et al. Effect of oximetry on hospitalization in bronchiolitis: a randomized clinical trial. JAMA. 2014;312(7):712–718. doi:10.1001/jama.2014.8637. PMID: 25138332.
4. Hartling L, Bialy LM, Vandermeer B, et al. Epinephrine for bronchiolitis. Cochrane Database Syst Rev. 2011;(6):CD003123. doi:10.1002/14651858.CD003123.pub3. PMID: 21678340.
5. Sigurs N, Gustafsson PM, Bjarnason R, et al. Severe respiratory syncytial virus bronchiolitis in infancy and asthma and allergy at age 13. Am J Respir Crit Care Med. 2005;171(2):137–141. doi:10.1164/rccm.200406-730OC. PMID: 15516534.
6. Borland ML, Loveys K, Babl FE, et al.; PREDICT Network. Australasian Bronchiolitis Guideline: 2025 Update. J Paediatr Child Health. 2025;61(8):1197–1215. doi:10.1111/jpc.70144. PMID: 40685806.
7. Moon RY, Carlin RF, Hand I; Task Force on Sudden Infant Death Syndrome and Committee on Fetus and Newborn. Sleep-Related Infant Deaths: Updated 2022 Recommendations for Reducing Infant Deaths in the Sleep Environment. Pediatrics. 2022;150(1):e2022057990. doi:10.1542/peds.2022-057990. PMID: 35726558.