When we start to feel sniffly, achy or feverish, it’s tempting to reach for supplements like echinacea and vitamin C, or other home remedies like nasal irrigation, to help keep flu-like symptoms under control.
In studies, cold and flu symptom treatments tend to show small effects, or sometimes none at all. That doesn’t mean they don’t work, says Reid Blackwelder, MD, FAAFP, professor and interim chair of the Department of Family Medicine at East Tennessee State University. When researchers evaluate treatments for cold symptoms, they’re “trying to find a really small difference for something that’s going to go away in a few days anyway.” So when a person begins to feel better, it’s hard to prove that the treatment is really responsible.
Here are some popular alternative treatments for cold and flu symptoms, and what we know about them.
Echinacea purpurea, the purple coneflower, is a popular supplement thought to boost the immune system and shorten the duration of upper respiratory symptoms like sinus congestion and sore throat.
A Cochrane review of 24 studies on echinacea and colds concluded that echinacea has not been shown to shorten or prevent colds, but also acknowledged that many trials showed small beneficial effects. These could be the result of bias or chance, but it’s also possible that the echinacea works and just has a very small effect.
Side effects are rare, according to the National Center for Complementary and Integrative Health, but people can have allergic reactions to echinacea, especially if they are also allergic to ragweed or its relatives, chrysanthemums, marigolds and daisies.
Zinc is a metal and a dietary mineral that our bodies require. People who don’t get enough zinc in their diet are more prone to infections, but zinc also seems to help, for unknown reasons, in shortening the duration of cold symptoms once a person is already sick.
A 2015 meta-analysis found that high-dose zinc lozenges that dissolve in the mouth can reduce the amount of time people spend dealing with runny noses, stuffy noses, coughs and muscle aches.
The author of that analysis, Harri Hemilä, MD, PhD, of the Department of Public Health at the University of Helsinki in Finland, points out that finding a good zinc lozenge is tricky. Some contain citric acid, which binds zinc ions. That means that little to no zinc may be available for a therapeutic effect. Zicam, Cold-Eeze and Walgreens generic zinc lozenges all contain zinc in a formulation that is likely to be more helpful than brands that include citric acid or similarly problematic ingredients like tartaric acid or mannitol.
Zinc lozenges, however, come with an annoying side effect: an unpleasant taste. More seriously, taking too much zinc can cause headaches, nausea and vomiting. Long-term high intake of zinc can cause your body to have trouble absorbing enough copper and can also depress the immune system. Blackwelder recommends limiting zinc supplements to no more than 25 mg per day to avoid overdosing.
3. Vitamin C
Vitamin C has a reputation as a major cold buster, and products like Emergen-C and Airborne use the vitamin in preparations aimed at preventing or treating cold symptoms. But despite this strong reputation, the evidence is mixed. A Cochrane review found that routinely taking vitamin C does not prevent colds, and the evidence was mixed on whether it could make colds shorter.
The dose of vitamin C necessary to help with cold symptoms is also unclear. Hemilä notes that doses of 6 g per day can be taken without side effects, while Blackwelder favors simply eating a diet high in fresh fruit.
The most common side effect of taking large doses of vitamin C is diarrhea, although Hemilä notes that it seems to cause this less often in people with colds than in healthy volunteers.
Garlic contains a chemical, allicin, that has antibacterial and antiviral properties when tested in the lab. To use it therapeutically, though, garlic would have to be taken as a pill or eaten in food, and it’s not clear if those antiviral properties would be able to make a difference to somebody suffering from cold or flu symptoms.
One trial found that people who took garlic were less likely to get colds than people who took a placebo, but a Cochrane review was not able to find any similar studies to compare it to. That means garlic sounds promising but doesn’t have a lot of evidence behind it.
Blackwelder points out that garlic supplements probably won’t be effective if they don’t have a garlic odor to them. The components of garlic thought to be responsible for its beneficial effect are the same ones responsible for its characteristic smell. Large doses of garlic can also cause a garlicky body odor, and can act similarly to aspirin to thin the blood.
5. Neti Pots (Nasal Irrigation)
A neti pot is a container with a spout like a teapot that can be used to flush the nose with warm salt water. If you can tolerate the odd feeling, nasal irrigation seems to help symptom relief, a Cochrane review concluded. There was not enough evidence to confirm whether irrigation shortens the duration of symptoms.
For severe congestion, Blackwelder says nasal irrigation may be a safer option than drugstore decongestants, which have side effects that can range from headache and restlessness to irregular heartbeat and trouble sleeping. If you find a neti pot uncomfortable, you can also accomplish nasal irrigation with a bulb syringe or a squeeze bottle. Side effects are limited to discomfort and irritation.
Beth Skwarecki is a freelance health and science writer based in Pittsburgh, PA