A common cold is a nonspecific, acute, self-limited infection of the upper respiratory tract. It more commonly occurs in children and most infections occur during fall and winter. Common cold is a viral infection of the upper respiratory tract, causing rhinorrhea, nasal obstruction, and coughing. Diagnosis is usually clinical and treatment is mostly symptomatic. The most important complication of common cold is secondary bacterial infection (e.g., pneumonia).
A nonspecific, acute, self-limited viral infection of the upper respiratory tract 
- Leading cause of ambulatory care visits in the US 
- More common in children 
- Seasonal pattern: Most infections occur during the fall and winter.
Epidemiological data refers to the US, unless otherwise specified.
- Viral infection 
- Rhinovirus (most common)
- Other viruses: parainfluenza, influenza, coronavirus, adenovirus, respiratory syncytial virus
- Transmission: direct contact, aerosols, and respiratory droplets
Infection of the nasal epithelium triggers the inflammatory response, which leads to: 
- ↑ Nasal blood flow and vascular permeability → rhinorrhea, congestion, and postnasal drip
- ↑ Concentration of leukocytes and their enzymes in the nasal mucosa → yellow–green nasal discharge
- Irritation of the upper airways → sneezing and coughing
Main symptoms: rhinorrhea, nasal obstruction, sneezing, and coughing 
- Symptoms typically resolve after 1 week.
- Cough may persist for 3 weeks.
- Other symptoms: sore throat, hoarseness, fever (uncommon), malaise, and fatigue
Physical examination finding
- Lungs are usually clear to auscultation
- Typically no prominent localizing features (e.g., facial pressure )
- Clinical diagnosis 
- Laboratory studies, viral detection techniques (e.g., antigen detection, PCR assays), and imaging are not routinely recommended.
- Allergic rhinitis
- Bacterial tonsillopharyngitis
- Infectious mononucleosis
- Tonsillitis, laryngitis
- See also “URTIs.”
The differential diagnoses listed here are not exhaustive.
- Symptomatic treatment: hydration, analgesics (e.g., acetaminophen, NSAIDs), and oral and/or topical decongestants (e.g., oxymetazoline, chlorpheniramine) 
- Antibiotics are not indicated unless a secondary bacterial infection is suspected.
- Extension of the viral infection to surrounding structures (e.g., ear, sinuses, larynx)
- Secondary bacterial infection, i.e., pneumonia (mostly due to S. pneumoniae, H. influenzae, M. catarrhalis, S. aureus)
- Exacerbation of asthma and/or chronic bronchitis
We list the most important complications. The selection is not exhaustive.