Many parents swear that sugary treats make their children overactive. (MARK LENNIHAN/ASSOCIATED PRESS)

As you think about decorating for the holidays, don’t worry about having poinsettias around. “Those beautiful flowers you’ve been so wary of keeping in your home during the holidays (lest they poison pets or children) are not toxic,” Live Science reports in “25 Medical Myths that Just Won’t Go Away,” citing a study that looked at nearly 23,000 cases of poinsettia exposure reported to poison control centers. None were fatal, and the most severe reactions were stomachaches.

This is just one of the supposed medical facts that the website knocks down as myth. (The poinsettia fears were probably sparked, Live Science writes, by a 1919 case in which a child was said to have died after eating parts of a poinsettia, but neither the death nor the poinsettia connection was ever confirmed.)

A few other seasonally relevant myths from this article:

Vaccines can cause the flu. No. The flu shot — have you gotten yours yet? — contains flu viruses, but they are not live. “A dead virus cannot be resurrected to cause the flu,” Rachel Vreeman, a doctor who has written about medical myths, told the website.

Cold weather makes you sick. No. People feel more chilled when it’s cold, but that does not translate into actually getting a cold, a major study found. “Whether . . . shivering in a frigid room or in an icy bath, people were no more likely to get sick after sniffing cold germs than they were at more comfortable temperatures.” We probably get more colds in winter just because there are more people stuck together indoors, making it easier to spread germs.

Sugar makes kids really wired. Nope, even though many parents swear this is true. Live Science writes: “In one particularly clever study, kids were given Kool-Aid sweetened with aspartame, a compound that contains no sugar. Researchers told half the parents the Kool-Aid contained sugar, and told the other half the truth.” Wrist sensors on the kids found they were “actually acting subdued,” but the parents who thought their kids had ingested a sugary drink “reported that their children were uncontrollable and overactive.” More likely it is the excitement of parties where sugary treats are served that makes kids wild.

Eating Thanksgiving turkey makes you drowsy. You will read stories about tryptophan, an amino acid found in turkey, and how it makes you want to nap — but, in fact, chicken and beef have pretty similar amounts of the chemical. Your sleepiness is probably just from overeating, with lots of carbohydrates and a few alcoholic beverages added in, experts told the website.

And, particularly relevant in a season of longer nights and more indoor activity:

Reading in the dark or sitting too close to the TV ruins your eyesight. These behaviors may tire your eyes because they work harder, but “there is no evidence that these practices cause long-term damage,” Vreeman told Live Science. However, she said, if you tend to sit so close to the TV (or computer) that your eyes hurt, it’s probably worth getting tested for nearsightedness.

— Margaret Shapiro