Croup is a common respiratory infection that primarily affects young children. It is almost always caused by a viral infection, most frequently the parainfluenza virus, which leads to swelling in the voice box and windpipe. This swelling narrows the airway, producing the distinctive, harsh, barking cough often described as sounding like a seal. While the symptoms can be alarming, most cases of croup are mild and manageable at home.
Duration and Timing of Croup Fever
The fever associated with croup is typically one of the shortest-lived symptoms of the illness. Croup often begins with symptoms similar to a common cold, including a low-grade fever, which usually lasts between 12 and 72 hours. This initial fever is commonly mild, generally staying below 102°F (38.9°C).
The disappearance of the fever does not signal the end of the infection. The hallmark coughing and breathing difficulties frequently intensify just as the fever starts to subside. If a fever persists beyond two days, or if the temperature rises significantly higher than 102°F, it may indicate a secondary bacterial infection, such as pneumonia, or a different diagnosis entirely.
The Overall Croup Illness Timeline
The overall timeline of croup extends past the initial fever period and is primarily marked by the progression of respiratory symptoms. The characteristic barking cough and the high-pitched, noisy breathing sound known as stridor usually begin developing within one to two days after the first cold-like symptoms appear. These airway symptoms tend to be at their worst roughly 24 to 48 hours after their onset. The most severe coughing and stridor frequently peak on the second or third night of the illness.
A defining feature of croup is that symptoms, particularly the cough, are characteristically worse at night due to natural changes in inflammation and airway positioning during sleep. While the fever may be gone quickly, the overall illness is self-limiting and generally lasts for about three to seven days. Full resolution of the cough may take up to a week or slightly longer in some cases.
When to Seek Medical Attention
While most cases of croup are mild, immediate medical attention is necessary if a child exhibits stridor—the harsh, crowing sound when breathing in—while they are resting or calm. Stridor at rest indicates a significant narrowing of the airway that requires prompt evaluation.
Other immediate red flags include signs of respiratory fatigue. This manifests as retractions, which is the skin pulling in around the ribs, breastbone, or neck with each breath as the child struggles to move air. A blue or gray tint to the lips or around the mouth, known as cyanosis, signals dangerously low oxygen levels and warrants an immediate emergency call.
Difficulty swallowing or excessive drooling should also trigger an emergency visit, as these symptoms may suggest a different, more serious condition like epiglottitis. Providing comfort and using fever-reducing medication is appropriate for mild symptoms, but never delay seeking emergency care if any of these severe breathing signs develop.