The common cold is a mild infection of the nose and throat, most often caused by rhinoviruses. These infections primarily affect the upper respiratory tract, leading to congestion, cough, sore throat, and sometimes a low-grade fever. When diarrhea occurs alongside these symptoms, it introduces confusion about the underlying illness. This gastrointestinal distress raises the question of whether the body is battling a single respiratory infection or a separate illness.
The Direct Answer: Diarrhea and the Common Cold
Diarrhea is not considered a common symptom of the classic common cold in adults. The viruses that cause the common cold target the respiratory system’s mucous membranes, not the intestinal lining. Therefore, a significant bout of diarrhea is highly unlikely to be caused by the cold virus itself.
Exceptions are sometimes seen in infants and young children. Certain viruses grouped with common cold causes, such as some strains of adenovirus, can cause both respiratory and gastrointestinal symptoms, including diarrhea, especially in children under five years old. In adults, mild gastrointestinal upset may occur indirectly due to swallowing excessive mucus from post-nasal drip, which can irritate the stomach. If diarrhea is severe, prolonged, or the most prominent symptom, the cause is almost certainly not a typical common cold.
Primary Illnesses That Cause Respiratory and Gastrointestinal Symptoms
When a person experiences both respiratory symptoms and diarrhea, it suggests an infection caused by a pathogen that affects both body systems. The most frequent culprit is often viral gastroenteritis, commonly mislabeled as the “stomach flu,” which is caused by viruses like norovirus or rotavirus. Norovirus infections are characterized by the rapid onset of vomiting and diarrhea, but they can also cause mild respiratory symptoms or body aches.
Influenza (The Flu)
Influenza is primarily a respiratory illness, but it can also cause gastrointestinal symptoms, particularly diarrhea and vomiting. This dual presentation is more prevalent in children than in adults. The symptoms of influenza are typically far more severe than a cold, often including high fever, fatigue, and significant body aches.
Other Viral Causes
Certain strains of coronaviruses, including the one responsible for COVID-19, are also known to cause both respiratory and digestive issues. While cough and fever are common with COVID-19, diarrhea is a recognized, though less frequent, symptom. Diarrhea can also be a side effect of medications taken to treat a cold, such as certain antibiotics or some over-the-counter cold remedies.
Key Differences: Distinguishing Symptoms and Onset
Distinguishing between a common cold and other illnesses involves looking closely at the severity and timing of symptom onset. Common cold symptoms tend to develop gradually over several days, beginning with a sore throat or runny nose. The hallmark of a cold is that symptoms are generally confined above the neck, and any associated fever is low-grade or absent.
In contrast, illnesses like influenza or viral gastroenteritis often strike suddenly. Influenza is frequently accompanied by a high fever, usually over 100.4°F (38°C), and intense body aches that are rare with a cold. Significant abdominal pain or cramping points strongly toward a gastrointestinal infection like norovirus, which is centered on the digestive tract.
If diarrhea is the most severe or dominant symptom, occurring frequently and aggressively, it suggests a primary infection of the gut. Conversely, if respiratory symptoms like congestion are the most prominent issues, and the diarrhea is mild or transient, the cause may be a secondary effect. The speed of onset and the location of the most intense discomfort are the most practical indicators for differentiating these illnesses.
When to Seek Medical Attention
While most acute episodes of diarrhea and respiratory illness resolve on their own, certain red flags necessitate immediate medical evaluation. The most significant danger associated with severe diarrhea is dehydration, especially in young children and older adults. Signs of severe fluid loss include excessive thirst, a dry mouth, dizziness, and urinating much less frequently than normal, or having dark-colored urine.
Adults should seek medical attention if diarrhea lasts longer than two days without improvement, or if they develop a fever higher than 102°F (39°C). Other serious warning signs include the presence of blood or pus in the stool, black or tarry stools, or severe, unrelieved abdominal pain. For infants, a lack of wet diapers for three or more hours, a fever over 102°F, sunken eyes, or unusual lethargy are urgent indicators for professional care.