The Medical Minute: Medical myths, part 2

By John Messmer
Penn State Family and Community Medicine
Penn State Milton S. Hershey Medical Center
Penn State College of Medicine

It's amazing what people will believe just because "they say that ..." or the information includes the statement, "Doctors won't tell you this." The Internet has contributed to the proliferation of questionable "truths" through e-mail and Web sites, even as it has made it easier to check the accuracy of claims. Sometimes a myth seems reasonable when the medical basis for the problem is not understood. Here are some more medical myths:

-- "I can't be allergic to my cat; I've had it for years."
In order to develop an allergy, one must have the genetic propensity for it. When the immune system cells are exposed to something we are allergic to, antibodies develop. The antibodies attack what we are allergic to and the reaction that takes place causes the symptoms of allergies. In some cases, the development of antibodies takes place so quickly, that we react after one or two exposures. Other times, it takes many exposures over years to stimulate an allergic response. So, in someone who has the genetic makeup for cat allergy, it is because one has had the cat for years that an allergy has eventually developed.

-- "Colds and flu come from cold, wet weather."
Colds are caused by various types of respiratory viruses and the flu is due to infection with influenza virus. Influenza viruses begin circulating in December when it's cold and wet, but the weather itself does not cause the flu. Colds occur year round, but in the winter people tend to be indoors more where they can spread the virus to each other more easily causing more people to be ill. There is some evidence that when the membranes of our noses are cooler, viruses can multiply more readily, but if we do not come into contact with a virus, cold weather might cause hypothermia, but we won't get an infection. We usually infect ourselves with cold viruses by picking up the virus from other people's hands or from things they have touched. Then we touch our nose, eyes or mouth and place the virus into our systems, allowing the virus to make us sick.

-- "People can carry diseases without being sick."
OK, this one is true. Many of us carry Strep bacteria in our throats from time to time but are not ill. We can have tuberculosis without symptoms or with symptoms so mild we don't recognize them as signs of illness. Our intestines can carry parasites or hepatitis A viruses that have not yet caused us to appear ill. Many viral respiratory illnesses can be spread a few days before we become ill. This is why good hand-washing is important at all times, particularly in food handling, and why coughing and sneezing should be directed to the bend of our elbows rather than our hands as this minimizes the chance of spreading the infectious agents into the air or from our hands to other people.

-- "Don't cross your eyes or they might stay like that."
Each eye has six muscles attached that work together to move the eyeballs around. The eye sits in the eye socket surrounded by membranes that in combination with the muscles hold it in place. A nerve, artery and vein enter from the back. There is nothing in the eye socket that can trap the eye or prevent its movement. Perhaps this myth comes from the observation of strabismus, or crossed eyes. A person's eye may not look straight ahead if a muscle is too short or not in balance with the others. This is not caused by anything the person has done, but is usually present at birth. Depending on the degree of strabismus, corrective glasses or surgery fixes it. So, all those goofy things kids do with their eyes may be annoying, but their eyes will always return to normal (although they don't have to know that).

-- "Black coffee helps people sober up."
Alcohol impairs judgment and coordination from the first drink, even at levels below the legal limit for drunkenness. Coffee may partially overcome the sedating effects of alcohol, but it does not counteract the impairment alcohol causes nor does it help clear the alcohol from one's systems faster. When tested, people who had blood alcohol levels below the legal limit only had better concentration after coffee. Driving requires more than concentration. When driving, it's best not to drink rather than to rely on coffee.

-- "Living near power lines causes cancer."
The concern here is the electric field generated by the power line. People are exposed to electric fields constantly, starting with the electric field around the earth, which is a hundreds of times more powerful than the electric fields on the ground below power lines. Multiple studies have not shown an increase in the rate of any diseases in association with normal exposures from power lines, household wiring, televisions, home appliances and so on.

-- "Sneezing causes your heart to stop for an instant."
Sneezing first lowers then raises the pressure inside the sneezer's chest as the person first inhales deeply then out forcefully. That pressure change affects blood flow to the heart and is sensed by the blood pressure monitor in the neck arteries. The heart compensates by a slight change in rate, but it does not stop.

-- "Standing at attention with locked knees causes fainting."
Fainting can happen due to dehydration, during extreme heat or from emotional stress. If someone is ill and perhaps dehydrated from vomiting or diarrhea or from being out in the heat without enough liquids, fainting can occur. If the person standing at attention in these circumstances also tightens their leg muscles to lock the knees, the exertion raises blood pressure slightly. When that person relaxes, the blood pressure drops slightly but it might be enough to cause fainting in the face of illness or dehydration. An otherwise healthy person should have no ill effects.

-- "Pregnant women should avoid cats."
Cats can carry an organism called toxoplasmosis in their intestines. They contract it from eating rodents in the wild, and they excrete the toxoplasmosis in their feces. Toxoplasmosis can seriously affect a developing fetus if the pregnant woman contracts it so she should avoid handling cat litter if her cat goes outdoors. If the cat always stays inside and receives regular veterinarian care, there is almost no risk. Toxoplasmosis cysts can be in sandboxes and outside soil and can contaminate raw meat. Cooking kills the organism and hand-washing eliminates it, but pregnant women should be particularly careful gardening or preparing food to keep her hands clean to avoid infection. The cat can stay.

There are still more medical myths, believe it or not. Next week, medical myths, part 3.