Causes of Common Cold

A cold is caused by viruses - full stop. Not by cold weather, wet hair, or cold drinks, however firmly grandmothers disagree. Understanding the real causes shows what actually spreads it and what merely feels like it should.

The viruses

• Rhinoviruses: cause about half of all colds, peak in spring and autumn
• Ordinary coronaviruses: the common human ones (not COVID), winter pattern
• Adenoviruses, parainfluenza, RSV and others: fill the rest of the calendar Over 200 virus types means no lasting immunity - each cold is usually a new strain.

How it actually spreads

• Hands and surfaces: the virus rides on hands to the nose and eyes - touched a rail, then your face. Handwashing is the single strongest defense
• Droplets and aerosols: coughs, sneezes and close conversation, especially indoors
• Close contact: households, classrooms and offices pass colds around efficiently; children are the family distribution network

The weather myth, examined

Cold weather does not cause colds - viruses do. But winter genuinely helps them: people crowd indoors with closed windows, dry heated air dries the nose's protective mucus, and some cold viruses multiply slightly better in cooler nasal passages. So winter colds are real; the shiver-did-it explanation is not.

What lowers your guard

• Poor sleep: even a few short nights measurably raise cold susceptibility
• Heavy stress: prolonged stress hormones dampen immune vigilance
• Smoking: damages the airway lining's defense and makes colds longer and worse
• Overtraining without recovery: extreme exertion can briefly open a window for viruses

One-line summary

Colds come from 200+ viruses spreading through hands, surfaces and close indoor contact - winter, poor sleep, stress and smoking raise the odds, but cold weather itself infects no one.