Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Those suffering from flu or cold congestion do not need to avoid dairy because it does not increase mucus production. Drinking milk and/or consuming other dairy products does not increase mucus production.

Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Warts on human skin are caused by viruses that are unique to humans (human papillomavirus). Humans cannot catch warts from toads or other animals; the bumps on a toad are not warts.

Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Waking sleepwalkers does not harm them. While it is true that a person may be confused or disoriented for a short time after awakening, this does not cause them further harm. In contrast, sleepwalkers may injure themselves if they trip over objects or lose their balance while sleepwalking. Such injuries are common among sleepwalkers.

Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
In South Korea, it is commonly believed that sleeping in a closed room with an electric fan running can be fatal. According to the Korean government, "In some cases, a fan turned on too long can cause death from suffocation, hypothermia, or fire from overheating." The Korea Consumer Protection Board issued a consumer safety alert recommending that electric fans be set on timers, direction changed and doors left open. Belief in fan death is common even among knowledgeable medical professionals in Korea. According to Yeon Dong-su, dean of Kwandong University's medical school, "If it is completely sealed, then in the current of an electric fan, the temperature can drop low enough to cause a person to die of hypothermia." Although an air conditioner transfers heat from the air and cools it, a fan moves air to increase the evaporation of sweat. Due to energy losses, a fan will slowly heat a room.

Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Although it is commonly believed that most body heat is lost through a person's head, heat loss through the head is not more significant than other parts of the body when naked. This may be a generalization of situations in which it is true, such as when the head is the only uncovered part of the body. For example, it has been shown that hats effectively prevent hypothermia in infants.

Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Eating less than an hour before swimming does not increase the risk of experiencing muscle cramps or drowning. One study shows a correlation between alcohol consumption and drowning, but there is no evidence cited regarding stomach cramps or the consumption of food.

Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
A person who is drowning does not always wave and call for help. In the final stages, raising the arms and vocalising are even usually impossible due to the instinctive drowning response. The technical term for the situation where a drowning person is capable of waving and calling for help is aquatic distress.

Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Contrary to a widespread perception, the real number 0.999...—where the decimal point is followed by an infinite sequence of nines—is exactly equal to 1 by definition. They are two different ways of writing the same real number. A 2009 study by Weller et al. states that "Tall and Schwarzenberger (1978) asked first year university mathematics students whether 0.999... is equal to 1. The majority of the students thought that 0.999... is less than 1." Weller et al. go on to describe their own controlled experiment, performed "during the 2005 fall semester at a major research university in the southern United States. Pre-service elementary and middle school teachers from all five sections of a sophomore-level mathematics content course on number and operation participated in the study." The results are striking: "On the question of whether .999...=1, 72% of the control group and 83% of the experimental group expressed their view that .999... is not equal to 1."

Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
The Coriolis effect does not determine the direction that water rotates in a bathtub drain or a flushing toilet. The Coriolis effect induced by the Earth's rotation becomes significant and noticeable only at large scales, such as in weather systems or oceanic currents. In addition, most toilets inject water into the bowl at an angle, causing a spin too fast to be significantly affected by the Coriolis effect.