Croup is a common childhood respiratory infection characterized by inflammation in the voice box and windpipe, resulting in the distinctive barking cough and noisy breathing known as stridor. Diarrhea is not a direct symptom of the airway inflammation that defines croup. However, the respiratory infection can coincide with or indirectly lead to digestive distress, often due to the specific infectious agents responsible for the illness.
Viral Etiology: The Indirect Link
Croup is primarily a diagnosis of the upper airway, but it is almost always triggered by a virus. The most frequent culprits are the Human Parainfluenza Viruses (HPIVs), especially types 1 and 2. These viruses, along with others that can cause croup, like Adenovirus or Respiratory Syncytial Virus (RSV), are not strictly limited to the respiratory tract.
Certain strains of these common respiratory pathogens can cause systemic symptoms, including affecting the gastrointestinal tract. Parainfluenza virus infections frequently list vomiting and diarrhea as possible symptoms. Adenoviruses are also a common cause of gastroenteritis, which presents with watery diarrhea and abdominal cramps. When a child has both the barking cough and diarrhea, it is likely the underlying virus is affecting two different body systems simultaneously.
Other Factors Contributing to Diarrhea
Diarrhea during an episode of croup may be due to factors separate from the primary viral trigger. A child can easily contract a separate viral gastroenteritis, commonly known as a stomach bug, at the same time they develop croup. Co-infections are common in young children, where pathogens spread easily in shared environments.
The use of antibiotics is another potential cause for a change in bowel habits. While croup is viral, antibiotics may be prescribed if a secondary bacterial infection, such as bacterial tracheitis, is suspected. Antibiotics disrupt the healthy balance of gut flora in the intestines, which can lead to antibiotic-associated diarrhea. This side effect is typically mild but affects approximately one in five children who take these medications. Corticosteroids, such as dexamethasone, are often given to treat airway swelling and can occasionally cause stomach upset, vomiting, or abdominal discomfort.
Hydration and Warning Signs
When diarrhea accompanies a respiratory illness, the risk of dehydration increases significantly, requiring close monitoring by parents. Mild to moderate dehydration is recognizable by signs like a dry mouth and lips, increased thirst, and decreased urination. In infants, this means fewer than six wet diapers over 24 hours, or in older children, no urination for eight hours.
Parents should offer fluids frequently in small amounts, ideally using an oral rehydration solution to replace lost electrolytes. Severe dehydration is a medical emergency that can present with significant lethargy or excessive sleepiness, sunken eyes, and a sunken soft spot (fontanelle) in infants. The skin may appear cool or mottled, and the child might be breathing rapidly.
Immediate medical attention is necessary if a child with croup and diarrhea exhibits blood in the stool, particularly if it appears dark, tarry, or maroon. Severe, localized abdominal pain, or an inability to keep any fluids down due to persistent vomiting, are also urgent warning signs. If a child is difficult to wake or is not producing tears when crying, these symptoms indicate a progression to severe dehydration that requires professional treatment.