The common cold has no cure, and its symptoms can last for one to two weeks. If you catch a cold, you can't do much about it but stay comfortable and hydrated. That's where honey and lemon come in. Prepared with warm water, they make a soothing drink that can ease your discomfort. The scientific proof for this is thin, but generations of cold sufferers seem to agree -- honey and lemon really work.
The National Institutes of Health calls lemon water with honey "a time-tested remedy" for a sore throat. Honey and lemon are not cures for a cold -- nothing but time is known to "cure" a cold. Still, this remedy is a viable alternative to over-the-counter medicines that can be costly and have side effects, and it provides a natural, soothing effect that can ease discomfort.
Honey and Coughs
Honey has a proven effect on throat irritation and coughs. A 2007 study published in "Archives of Pediatric and Adolescent Medicine" found that a single dose of honey was consistently rated highest by parents whose children suffered from a night cough -- higher than honey-flavored dextromethorphan, a common cough syrup additive. A 2010 review of this study published in "Cochrane Database of Systematic Reviews" found that honey was effective at reducing cough frequency and improving sleep quality, and that it may be equally effective to dextromethorphan. This is not to say that honey is always effective for all children with a cough. Nonetheless, honey's soothing effect on the throat may have real benefit and is likely safe if your child has a simple cold. Never give honey to an infant younger than 1 year, however, as it carries a risk of botulism.
Lemon and Health
The connection between lemon and the common cold has not been fully studied. Its acidity may loosen mucus, but the NIH reports that evidence is conflicting on whether vitamin C truly has an effect on colds. A 2007 review of 30 different studies, published in "Cochrane Database of Systematic Reviews," found that vitamin C megadoses do not appear to prevent or relieve colds for most people. The amount of vitamin C in a single lemon is far less than you'd find in a vitamin C supplement, so it's very unlikely that lemon water will cure your cold in any way.
All scientific evidence aside, there's a reason people have been quaffing warm lemon and honey brews for generations. The flavor and scent are soothing and pleasant, and the effect on a cold-ridden throat is comforting at least. As with all things, exercise moderation and talk to your doctor if your symptoms fail to improve or get worse.