Cough occurs when the lungs' airways are irritated. How to manage a cough depends on the cause.
A typical cold may cause a cough for up to 2 weeks, and although frustrating to the parents, a simple cold cough is not dangerous and will pass on its own. Over-the-counter cough medications have limited effectiveness and may not be worth the side-effects (or fight the child puts up!), but some kids may benefit a little. There is no convincing evidence that one OTC medicine is better than the other. Some doctors and nurse practitioners will prescribe cough medications with narcotics in them. In the older child or adolescent who has been sleepless for 2 nights (because of cough), these medications may be worthwhile. There are, however, risks of drowsiness, allergic reactions, and abuse. Remember that suppressing the cough does not cure the illness, it is only masking symptoms.
Not all coughs are due to a simple cold. If your child has labored or rapid breathing with the cough, pneumonia, asthma, and foreign body in an airway need to be considered. Have him/her seen as soon as possible.
Any newborn with a cough should be seen as soon as possible. Considerations are pneumonia, whooping cough, or RSV bronchiolitis. If your baby gags with feeds, is unusually fussy, or arches his/her back alot, gastroesophageal reflux (stomach acid coming up) may be the cause of cough and he/she should be seen.
Some children who seem to have coughs lasting a few weeks with every cold may in fact be asthmatic. Prolonged cough, cough worse at night, cough with exercise, and cough with laughing or crying could be signs of asthma, even if there is no wheezing. If you suspect this, your child should be evaluated. Cough suppressants can actually be bad for a child coughing because of asthma; they need asthma therapy.
Foreign body ingestion or aspiration should not be overlooked as a cause of cough, especially in a toddler or small child. Coins, marbles, etc. can get lodged in an airway or the esophagus, causing cough. If it is a major airway that's blocked the child may have labored breathing, but if it's a smaller airway he/she may have cough only. If your child's cough had a rather sudden onset or was preceded by a choking or gagging episode, have him/her seen by your doctor.
Some children whose cold symptoms fail to improve or get worse after 2 weeks may receive antibiotics for bacterial sinusitis (viral sinusitis does not respond to antibiotics). If your child has received antibiotics for sinusitis 2 or more times, an underlying cause needs to be investigated (for example immune deficiency, cystic fibrosis, enlarged adenoids, and severe allergies).
Allergies alone do not cause cough. Allergies may stimulate cough in an asthmatic, however. Typical allergy symptoms include sneezing, stuffy nose, itchy nose, itchy throat, itchy ears, and itchy/watery eyes. Therefore it is unlikely antihistamines will cure a cough.