Symptoms of a common cold usually appear one to three days after exposure to a cold-causing virus. Signs and symptoms, which can vary from person to person, might include:

• Runny or stuffy nose
• Sore throat
• Cough
• Congestion
• Slight body aches or a mild headache
• Sneezing
• Low-grade fever
• Generally feeling unwell (malaise)

The discharge from your nose may become thicker and yellow or green in color as a common cold runs its course. This isn't an indication of a bacterial infection.

Although many types of viruses can cause a common cold, rhinoviruses are the most common culprit.

A cold virus enters your body through your mouth, eyes or nose. The virus can spread through droplets in the air when someone who is sick coughs, sneezes or talks.

It also spreads by hand-to-hand contact with someone who has a cold or by sharing contaminated objects, such as utensils, towels, toys or telephones. If you touch your eyes, nose or mouth after such contact or exposure, you're likely to catch a cold.

These factors can increase your chances of getting a cold:

• Age. Children younger than 6 are at greatest risk of colds, especially if they spend time in child-care settings.
• Weakened immune system. Having a chronic illness or otherwise weakened immune system increases your risk.
• Time of year. Both children and adults are more susceptible to colds in fall and winter, but you can get a cold anytime.
• Smoking. You're more likely to catch a cold and to have more-severe colds if you're exposed to cigarette smoke.
• Exposure. If you're around many people, such as at school or on an airplane, you're likely to be exposed to viruses that cause colds.

• Acute ear infection (otitis media). This occurs when bacteria or viruses enter the space behind the eardrum. Typical signs and symptoms include earaches and, in some cases, a green or yellow discharge from the nose or the return of a fever following a common cold.
• Asthma. A cold can trigger an asthma attack.
• Acute sinusitis. In adults or children, a common cold that doesn't resolve can lead to inflammation and infection of the sinuses (sinusitis).
• Other secondary infections. These include strep throat (streptococcal pharyngitis), pneumonia, and croup or bronchiolitis in children. These infections need to be treated by a doctor.