Cold comfort

The cold is as common as ever, but a good remedy is hard to find.

The cold season has arrived, a cure hasn't, and even efforts at treating the symptoms seem like a dubious proposition these days.

Over-the-counter cold remedies have come under harsh scrutiny lately. In October 2007, an FDA advisory panel recommended a ban on cold medicines for children under six, and in anticipation of that vote, several drug makers pulled their infant cold medicines off the shelves. Medicines for adults weren't affected, but they don't have a track record that inspires great confidence. A drug called phenylpropanolamine was used as a nasal decongestant in many products until researchers linked it to hemorrhagic strokes in women. Guidelines from the American College of Chest Physicians in 2006 cast doubt on the effectiveness of cough expectorants and suppressants included in many over-the-counter products.

Little wonder, then, that people have sought out alternatives like vitamin C and zinc. But for the most part, the evidence for them is pretty shaky.

Here's a rundown on cold treatment and prevention:

Over-the-counter medicines. Colds, of course, have a variety of symptoms, so cold medicines have a variety of ingredients: almost always some kind of pain and fever reducer, usually acetaminophen; a cough suppressant, often dextromethorphan; a nasal decongestant, usually phenylephrine; and sometimes an antihistamine, often chlorpheniramine. We've posted a list of over-the-counter (OTC) cold medicines and their ingredients on our Web site at www.health.harvard.edu/health.

The combination of uncertain benefit and possible harm cast a shadow over the infant and children's cold formulations. Do these concerns apply to the adult medicines? Efficacy is certainly an issue. The American chest physicians aren't alone in their skepticism about the anticough ingredients. British researchers reviewed 15 trials of cough medicines and concluded that "there's no good evidence of their effectiveness." Their damning assessment included antihistamines. The first-generation antihistamines like doxylamine and chlorpheniramine have a sedating effect, so they're often ingredients in the medicines that brag about nighttime relief.

If taken at the recommended dose, the OTC medicines are reasonably safe for adults. Still, that's a sizable if. Most of the complications from the infant and children's formulations have come from accidental overdoses, which can be a problem for adults, too. People don't necessarily read the fine print and may not realize, for example, that a tablespoon of Nyquil contains 500 milligrams (mg) of acetaminophen. If they are taking lots of Tylenol — which is acetaminophen — at the same time, they can get into trouble that, in the worst case, may end in liver failure.

The possibility of anticholinergic effects from antihistamines is also something to keep an eye on. Particularly in older people, anticholinergic drugs can cause confusion, constipation, urinary retention, and other problems.

Pseudoephedrine, the active ingredient in stand-alone nasal decongestant products like Sudafed, is a powerful medicine that needs to be taken with care. It works by constricting nasal blood vessels, but that effect isn't limited to the nose. Pseudoephedrine can cause hypertension and, rarely, cardiac arrhythmias and strokes, as well as urinary retention in men with an enlarged prostate gland. It's unclear whether phenylephrine, the nasal decongestant that has replaced pseudoephedrine in many of the multisymptom cold medicines, poses the same risk.

Vitamin C. Linus Pauling's book, Vitamin C and the Common Cold, was published in 1970. The Nobel laureate believed that most people should take 1,000 to 2,000 mg of vitamin C daily, advised people to carry a 500-mg tablet at all times to take at the first sign of a cold, and envisioned eradicating colds from certain parts of the world within a decade or two. In 2007, a review of 30 trials that included a total of over 11,000 people found that taking the vitamin to prevent colds had little, if any, effect. Exceptions might be people who engage in heavy-duty exercise like marathon running or who are exposed to extreme cold. Such experiences cause temporary dips in immune function that vitamin C may offset. Whether megadoses might help treat a cold once it's started will require more research, the review concluded.

Zinc. Taking zinc has been proposed as a way to shorten colds and perhaps reduce their severity. The mineral's cold-fighting career got started with a 1984 report by a Texas researcher, George Eby, that zinc lozenges shortened colds by seven days. The research has meandered since, with some positive outcomes and some negative ones. Stanford researchers reported in 2007 that three of four studies that they identified as being the most reliable didn't find a therapeutic benefit from zinc lozenges or nasal spray. The fourth, which tested a nasal gel, did. There have been several reports, though, of zinc gels causing a loss of the sense of smell. In most cases, the sense comes back, but the impairment has been known to last more than six months.

Echinacea. Gardeners know echinacea as the coneflower, a perennial that looks a little like a daisy, but has thin, droopy petals. In a meta-analysis of 14 studies, University of Connecticut researchers found that taking echinacea decreased the odds of developing a cold by 58% and the duration by 1.4 days. The results, reported in 2007 in Lancet Infectious Diseases, were a bit surprising because a number of randomized clinical trials, including two funded by the National Institutes of Health, hadn't found any benefit from taking echinacea. Meta-analyses are a good way to get a handle on a body of evidence, but there are always questions about the quality of the underlying studies, how results are weighted, and the variety of doses used.

Prevention that works

Only a small percentage of sneezes and coughs contain cold viruses, so you're more likely to spread — or pick up — cold viruses by way of your hands. Regular handwashing really is one of the best cold protection tactics around. Exercising very hard may temporarily lower your immunological guard, but regular, moderate exercise boosts the immune system, and some research suggests it could prevent colds. Hopes for vitamin D are running sky-high these days, with research suggesting that it may have anticancer effects. It may also help fend off colds by boosting the immune system. But don't go overboard. The safe daily upper limit for vitamin D is 2,000 International Units.

And once you get a cold...

Cold medicines aren't the only OTC game in town. You can take many of the ingredients contained in these medicines separately, which allows for a targeted rather than a shotgun approach to symptoms. Aspirin or acetaminophen can ease the pain of a sore throat. Nonsteroidal anti-inflammatory drugs like naproxen (Aleve, other brands) can help with a cough.

Taking a decongestant isn't the only way to open up nasal passages. Inhaling steam from a teakettle or in a hot shower can help. Drinking plenty of water helps unplug nasal passages by keeping mucus moist and flowing. And if you have a fever, fluids counteract the tendency to get dehydrated.

Finally, don't overdo the nose blowing. Too much blowing can push nasal fluids laden with bacteria and viruses into the sinus cavities. The result in some cases is a secondary infection of the sinuses that needs to be treated with antibiotics.