The common cold is a common respiratory illness affecting the nose, throat, and sinuses. Diarrhea is a digestive issue involving loose, watery stools. While these conditions affect different systems, some individuals experience them concurrently, raising questions about a connection.
Understanding the Common Cold and Diarrhea
The common cold is a viral infection of the upper respiratory tract. It is most frequently caused by rhinoviruses, though over 200 different viruses, including certain coronaviruses, can be responsible. These viruses affect the respiratory mucosa of the nose, throat, sinuses, and larynx.
Diarrhea is defined as passing three or more loose, watery bowel movements in a single day. It is a symptom of a digestive system issue, often an intestinal infection caused by viruses, bacteria, or parasites. The viruses responsible for the common cold do not directly cause diarrhea.
Why Diarrhea Might Accompany a Cold
Diarrhea accompanying a cold is usually due to indirect factors, not the cold virus itself. One explanation is co-infection, where a person contracts both a respiratory virus (causing the cold) and a separate gastrointestinal virus or bacterium. Viruses such as norovirus or rotavirus are known causes of gastroenteritis, or “stomach flu,” which targets the digestive system and leads to diarrhea.
Medication side effects can contribute to digestive upset during a cold. Some over-the-counter cold remedies, especially those with decongestants, can cause gastrointestinal disturbances like mild nausea or diarrhea. If a cold leads to a secondary bacterial infection requiring antibiotics, these medications frequently cause diarrhea due to their impact on gut bacteria.
Post-nasal drip is another potential, less common, reason for gastrointestinal symptoms. During a cold, excessive mucus can drain down the back of the throat. If swallowed, this mucus can irritate the stomach and digestive tract, potentially leading to nausea, vomiting, or diarrhea.
The body’s immune response to an infection can play a role. When fighting a cold virus, the immune system triggers inflammatory responses. This systemic inflammation can influence gut motility, leading to changes in bowel habits. This mechanism is less direct and typically results in milder digestive symptoms.
When to Be Concerned and Seek Medical Advice
While mild diarrhea with a cold is often temporary, certain signs warrant medical attention. Symptoms of dehydration, such as reduced urination, excessive thirst, dry mouth, or dizziness, indicate a need for professional evaluation, as severe dehydration can lead to complications. For adults, diarrhea lasting more than two days, or for children, not improving after 24 hours, should prompt a doctor’s visit.
Other concerning indicators include a high fever, especially if it exceeds 102 degrees Fahrenheit (39 degrees Celsius) or persists for more than three days. The presence of bloody or black stools, severe abdominal pain or cramping, or symptoms that worsen instead of improve are also red flags. Individuals with underlying health conditions or weakened immune systems should seek advice promptly if they experience diarrhea with a cold, as they may be more vulnerable to complications.