Coughing is a normal mechanism used to help clear your throat or keep the lungs clear. There are different types of coughs, such as dry or productive. A productive cough brings up mucus or phlegm from your lungs. For a 3-year-old, a cough is a normal part of childhood illness but can be a sign of a serious medical condition if it persists. There are various remedies to treat a cough, but they are not a substitute for medical treatment. Consult with your health-care provider to discuss any potential risks.
Drinks
Drinking plenty liquids, such as juice, water and clear broth aids as an expectorant, which can loosen a dry, hard cough to help expel phlegm, according to Dr. Robert Beckerman, a professor of pediatrics and physiology and section chief of pediatric pulmonology at Tulane University School of Medicine in New Orleans. In addition, Dr. Blake Noyes, an assistant professor of pediatrics in the Division of Pulmonology at the Children's Hospital of Pittsburgh, states that drinking a hot drink can help soothe your child when she has a cough caused from a dry throat from breathing through her mouth.
Humidifier
A cool-mist humidifier or vaporizer can help increase the moisture in the air, which may help improve congestion and other symptoms related to a cough, including colds, allergies and asthma. However, Dr. Robert Beckman mentions that although adding humidity with a vaporizer seems sensible, vaporizers are a breeding ground for mold and bacteria because they are hard to clean and could make the coughing condition worse.
Steam
If your child has a "barky" or "croupy" cough, steaming up the bathroom with the hot water turned on and sitting in the bathroom with him for approximately 20 minutes will help him breathe easier, according to Kids Health. The steam works to loosen the congestion, which is the cause of the cough.
OTC Cough Remedies
An over-the-counter cough medicine that contains an expectorant may help loosen the mucus build-up in your child's lungs. However, depending on the cause of the cough, it may not be the appropriate medical treatment. Consulting with your child's pediatrician before administering the medication is advisable to ensure the effectiveness, safety and dosage. In addition, Dr. Naomi Grobstein, a family physician in Montclair, New Jersey, states that a cough medicine containing dextromethorphan and guaifenesin may help loosen mucus and provide mild cough relief, but you should not attempt to suppress a cough entirely. Before administering a cough medicine to your child, consult with your health-care provider to discuss potential risks.
Medical Visit
According to Kids Health, viruses cause most coughs, and a doctor will usually not treat the cough and let the virus run its course, which will generally last up to two weeks. However, if your child's cough is persistent, he is having trouble breathing or you notice a crackling noise in his lungs, seek medical attention.


