If a sore throat, stuffy nose, sneezing, and headache aren’t enough to make you feel miserable from a cold or other acute upper respiratory infection this winter, you may also experience an annoying cough that disrupts your sleep and makes your chest hurt even more. It’s logical to want to try a cough syrup or other over-the-counter cough medicine—and drugstore shelves are lined with them.
There are two general categories of OTC medicines for cough related to acute respiratory infections: antitussives (typically used to suppress a “dry” cough) and expectorants (used to help bring up phlegm in “productive” coughs).
Dextromethorphan, which has been around since the late 1950s, is the most common antitussive ingredient in OTC cold medicines. This single ingredient can be found, for example, in Robitussin Long-Acting CoughGels and Vicks Formula 44 Cough Control. It’s not clear how dextromethorphan might work, but it’s been proposed that it affects the brain’s cough center (located in the brain stem), making it less likely that you’ll easily or readily cough. Possible side effects of dextromethorphan include nausea, drowsiness, and dizziness. Also, this drug can be abused, leading to feelings of euphoria if taken in high doses.
If, on the other hand, you are bringing up or trying to bring up phlegm, you may be told to (or think you should) take an expectorant. The only ingredient approved by the FDA as an expectorant in OTC cough medicines is guaifenesin, such as found in Mucinex and Robitussin Cough and Chest Congestion DM. Use of this medicinal substance dates back centuries to Native Americans, who extracted it from the guaiac tree. It’s not clear how guaifenesin might work, either, but it may thin mucus in the respiratory tract, making it easier to cough up the mucus. Side effects from guaifenesin are uncommon but may include headache, dizziness, and nausea.
Some OTC cough medicines have multiple ingredients. Alka-Seltzer Plus Severe Cold and Flu contains dextromethorphan plus an antihistamine and a decongestant. Antihistamines are added to suppress the postnasal drip that often accompanies a cold and contributes to coughing. Decongestants are added with the thought that they might relieve the stuffy nose that also often accompanies a cold. These extra ingredients have their share of side effects, too: Antihistamines can cause sleepiness, dry mouth, and impaired ability to urinate, for instance, while decongestants can interfere with sleep and trigger anxiety and tachycardia (fast heart rate).
But do they actually work?
Despite all the cough medicines on the market, you may be surprised to know that there doesn’t appear to be any solid evidence for their use.
A 2014 systematic review by the Cochrane Collaboration of 29 randomized controlled trials looked at the effect of OTC cough medications on more than 4,800 adults and children with acute cough. The medicines included antitussives, expectorants, antihistamines, and decongestants, alone or in various combinations. According to the authors, the studies had conflicting findings, and coughs often resolved in a few days whether participants took medicine or a placebo. Moreover, 21 studies reported adverse effects, especially from dextromethorphan. The results “have to be interpreted with caution,” however, the authors wrote, because there were only a few studies in each category of cough medicine. In addition, the methodology of the studies varied a lot and was not always adequately reported, and some studies were funded by pharmaceutical companies (which tended to report more favorable results).
And in 2017, an expert panel evaluated studies involving nearly 6,500 people who had acute cough associated with the common cold. Their report concluded that there was no reason to recommend OTC cough-relieving products because the evidence was lacking that they helped resolve coughs faster or made them less severe.
Still on drugstore shelves
So, if there’s no conclusive evidence that OTC cough medicines work, why are they still sold? The FDA approved dextromethorphan a long time ago based on old studies (mostly from the 1950s) showing that it worked—modestly at best—for coughs that were either experimentally induced in people who were healthy or in those who had a chronic illness, such as tuberculosis. And the methodologies at that time, which didn’t always include placebo control groups, were not as rigorous as would be used nowadays. Since then, the FDA has not taken any action to pull this ingredient, or other questionable cough medicine ingredients, from the market.
BOTTOM LINE. To help subdue an acute cough from an infection, you might consider trying some of the home remedies described in the box below rather than opting for cough medicine. Though the cough can linger for a long time, it should start to improve after a week or so, with or without intervention. If it doesn’t improve after a couple of weeks, see your doctor. You should also seek medical advice if the cough progressively worsens and is associated with fever or shortness of breath.
If you have an acute cough, you can try some non-drug remedies, though definitive evidence of benefits from studies (several dating back some time) is also lacking. Still, there’s little or no risk of serious adverse effects, and if they work for you, that’s all that really matters.
- Honey. It’s been proposed that honey, because of its thickness, may coat sensory receptors in the throat, sending signals to the brain that interfere with the need to cough. It may also soothe the back of the throat. A 2018 Cochrane review involving children with acute cough concluded that honey was “probably” more effective than some OTC meds and better than no treatment or placebo—but not as effective as dextromethorphan (for which there is no solid evidence either).
- Vicks VapoRub. The combination of aromatic ingredients in this ointment, including menthol and eucalyptus oil, may activate a receptor in the airways to decrease the sensitivity of the cough reflex. In a study of 138 children who had nighttime cough and congestion due to an upper respiratory infection, the researchers compared the effects of a parent rubbing either Vicks or a petrolatum (control) product on the child’s neck and chest before sleep. The parents rated the Vicks product as better for reducing cough, congestion, and problems sleeping.
- Hot beverages. Sipping a hot beverage may provide some cough relief, according to a small study of 30 people with symptoms of a common cold or flu who drank a blackcurrant cordial. This, the authors say, may be due to a “physiological” effect of the hot drink, whereby its taste, smell, and temperature promote saliva production and mucus secretions to lubricate and soothe the upper airways—or to a placebo effect.
- Water. Making sure you drink plenty of water may help lessen coughing, at least according to a 2022 study of adolescents with asthma.
- Steam inhalation. Anecdotal reports—but a lack of clinical studies—suggest that breathing in steamed air may help relieve cold-related coughs by thinning the mucus in the nose that is contributing to the cough. This can be done by leaning over a bowl of just-boiled water with a towel over your head and, with your eyes closed, inhaling slowly through your nose for five to 10 minutes. It’s generally safe to do this several times a day if you are careful to not let the hot water and steam burn you (don’t get too close). A possibly safer alternative is to simply sit in a steamy bathroom.
