A cold is caused by a virus. There are more than 200 different types of viruses that can cause a cold. The most common one is called the rhinovirus, but others include the coronavirus, parainfluenza, adenovirus, enterovirus, and respiratory syncytial viruses.
Once a virus enters your child's body, it causes a reaction — the body's immune system begins to react to and fight off the foreign virus. This, in turn, causes:
- An increase in mucus production (a runny nose)
- Swelling of the lining of the nose (making it hard to breath and congestion)
- Sneezing (from the irritation in the nose)
- Cough (from the increased mucus dripping down the throat)