The Ache: Cold and flu season is here, and with it, a healthy dose of misery.

The Claim: Echinacea, a herbal remedy made from a flowering plant, can prevent respiratory infections—or even help treat them once they begin.

The Verdict: A study in 2015 found a hot drink containing echinacea to be as good as prescription Tamiflu for treating influenza, and a large 2012 study found the remedy cut down on the number of days suffered with colds. The results don’t apply to all formulations of echinacea, which can vary widely, and scientists caution that people at high risk for flu complications shouldn’t forgo more-tested prescription medications.

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“If you are getting plenty of fluids and plenty of rest and you want to take echinacea, it seems like a reasonable thing to do and unlikely to harm you,” says Pritish K. Tosh, associate professor at the Mayo Clinic in Rochester, Minn. But people at risk for flu complications, such as pneumonia or bronchitis, should instead take an antiviral medication such as Tamiflu, he adds. Risks for complications are elevated in people 65 years and older or those with chronic health conditions, such as asthma or heart disease, according to the Centers for Disease Control and Prevention.

Echinacea—long debated as a possible nostrum for colds and flus—is typically sold as capsules or as a tincture, or alcohol extract, which can be mixed with water and taken several times daily. Laboratory research suggests the herbal remedy may hamper the ability of viruses to infect a host. It also may regulate the immune system, either by stimulating it or preventing an overreaction responsible for symptoms, scientists say.

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