While an occasional cough is normal, a cough that persists may be a sign of a medical problem.

A cough is considered "acute" if it lasts less than three weeks. It is considered "chronic" if it lasts longer than eight weeks (four weeks in children).

Some causes of coughs include:

Common causes — acute

• Common cold
• Influenza (flu)
• Inhaling an irritant (such as smoke, dust, chemicals or a foreign body)
• Pneumonia
• Whooping cough

Common causes — chronic

• Allergies
• Asthma (most common in children)
• Bronchitis
• Gastroesophageal reflux disease (GERD)
• Postnasal drip

Others

• Acute sinusitis
• Bronchiectasis, which leads to a buildup of mucus that can be streaked with blood and raise the risk of infection.
• Bronchiolitis (especially in young children)
• Choking: First aid (especially in children)
• Chronic sinusitis
• COPD
• Coronavirus disease 2019 (COVID-19)
• Croup (especially in young children)
• Cystic fibrosis
• Emphysema
• Heart failure
• Laryngitis
• Lung cancer
• Medications called angiotensin-converting enzyme (ACE) inhibitors
• Neuromuscular diseases that weaken the coordination of upper airway and swallowing muscles
• Pulmonary embolism
• Respiratory syncytial virus (RSV)
• Sarcoidosis (a condition in which tiny collections of inflammatory cells can form in any part of the body)
• Tuberculosis

Call your doctor if your cough (or your child's cough) doesn't go away after a few weeks or if it also involves any one of these:

• Coughing up thick, greenish-yellow phlegm
• Wheezing
• Experiencing a fever
• Experiencing shortness of breath
• Experiencing fainting
• Experiencing ankle swelling or weight loss

Seek emergency care if you or your child is:

• Choking or vomiting
• Having difficulty breathing or swallowing
• Coughing up bloody or pink-tinged phlegm
• Experiencing chest pain

Self-care measures

Cough medicines usually are used only when cough is an acute condition, causes a lot of discomfort, interferes with sleep and is not associated with any of the potentially worrisome symptoms indicated above. If you use cough medicine, be sure to follow the dosing instructions.

Over-the-counter cough and cold medicines are intended to treat the symptoms of coughs and colds, not the underlying disease. Research suggests that these medicines haven't been proved to work any better than inactive medicine (placebo). More important, these medications have potentially serious side effects, including fatal overdoses in children younger than 2 years old.

Don't use over-the-counter medicines, except for fever reducers and pain relievers, to treat coughs and colds in children younger than 6 years old. Also, consider avoiding use of these medicines for children younger than 12 years old.

To ease your cough, try these tips:

• Suck cough drops or hard candies. They may ease a dry cough and soothe an irritated throat. Don't give them to a child under age 6, however, because of the risk of choking.
• Consider taking honey. A teaspoon of honey may help loosen a cough. Don't give honey to children younger than 1 year old because honey can contain bacteria harmful to infants.
• Moisturize the air. Use a cool mist humidifier or take a steamy shower.
• Drink fluids. Liquid helps thin the mucus in your throat. Warm liquids, such as broth tea or lemon juice, can soothe your throat.
• Avoid tobacco smoke. Smoking or breathing secondhand smoke can make your cough worse.