Wait at least 30 minutes before swimming after eating. Eat garlic to prevent mosquito bites. Drink water from a garden hose. These well-intentioned but misguided pieces of advice have been circulating for generations. It’s time to set the record straight on some common summertime medical misconceptions.
#1: You can catch a cold from air conditioning.
False.
Colds are caused by viral infections, (primarily by the rhinovirus), not by sitting in an air conditioned room. Symptoms that mimic a cold — like irritated nasal passages or a scratchy throat — can result from prolonged exposure to dry, cooled air. A poorly maintained air conditioner may harbor dust and mold, triggering itchy eyes and sneezing in allergy sufferers. To avoid upper respiratory problems, use a cool mist vaporizer to increase room humidity, and change the air conditioner filter regularly.
#2: Eating garlic helps to prevent mosquito bites.
False.
A study published in the March 2005 Journal of Medical and Veterinary Entomology confirmed that garlic does not repel mosquitos. It’s better to wear long sleeves and pants, or use bug sprays like Sawyer’s 20% Picaridin Insect Repellant or Deep Woods OFF!
#3: Poison ivy is contagious.
False.
You can’t get poison ivy by touching an affected person’s rash; the liquid inside the skin blisters isn’t contagious, either. Poison ivy is caused by coming into contact with urushiol, a sticky, oily sap produced by the plant. By the time most victims have a rash, the urushiol has disappeared from the skin. But, beware: it can linger for up to a year on clothing, animal fur, or items like contaminated garden tools.
#4: You should wait 30 minutes after eating before you swim.
False.
This myth likely arose from fear that while the body’s blood is diverted to the gut during digestion— away from arm and leg muscles — the victim could develop cramps and drown. An extensive literature review in December, 2013 by the International Life Saving Federation found no scientific evidence to support this claim. No major medical and safety organization — including the American Red Cross — recommends waiting to swim after eating.
#5: Hop on one foot to get the water out of your ear after swimming.
False.
Persistent water in the ear is uncomfortable and may cause an infection (“swimmer’s ear” or otitis externa). But hopping on one foot doesn’t help. Instead, simply turn your head to the side and pull your ear up and back to let the water run out. Blowing into the ear canal with a hairdryer can help, too — but hold it far enough away from the outer ear to avoid burns. If these two methods fail, try “plunging” your ear: Tilt your head to the affected side, press your palm against your ear tightly enough to create a seal, then repeatedly flatten and cup your hand.
#6: Drinking out of a garden hose is safe.
False.
Standard garden hoses contain phthalates (chemical additives which improve plastic’s flexibility) and lead: Both can leach into water. Hoses are often a breeding ground for bacteria and mold, too. If you still want to drink from a garden hose, make sure it’s labeled “drinking water safe”, and flush out any stagnant water before drinking.
#7: Ice-cold drinks cool you down faster than hot drinks.
False.
Our bodies keep cool by sweat evaporation. Cold beverages suppress the body’s ability to perspire; hot drinks enhance it. So — as long as it’s not exceptionally humid (above 90%)— choosing a warm beverage will keep you cooler.
#8: Take shelter under a tree during a thunderstorm.
False.
According to the National Lightning Safety Council, standing under a tree is the second leading cause of lightning strike casualties — the first is engaging in water-related outdoor activities, such as boating, swimming, or fishing. If you are caught without shelter during a thunderstorm, immediately get away from bodies of water (like ponds and swimming pools), and off elevated areas (like hills and mountain ridges). Don’t lie flat on the ground — it conducts electricity. Instead, crouch down as low as possible, tuck your head and cover your ears with your hands until the lightning stops.
#9: The higher the SPF in sunscreens the better.
False.
Skin damage, such as sunburn, wrinkles, liver spots, and skin cancer, are caused by two types of ultraviolet (UV) light produced by the sun: UVA and UVB. Sun protection factor — SPF — specifically measures a sunscreen’s ability to protect the skin from UVB and sunburn. Sunscreens with an SPF of 100 block 99% of UVB rays — but that’s only 2% more than an SPF of 30, which blocks 97%. The American Academy of Dermatology recommends using a water-resistant, broad-spectrum product (which protects against both UVA and UVB), with an SPF of at least 30. Examples include Hydrating Sheer Sunscreen Broad Spectrum SPF 30 for Face & Body or Neutrogena Ultra Sheer Dry-Touch Sunscreen Lotion Broad Spectrum SPF 30. Sunscreen should be applied 30 minutes before going out into the sun; reapply at least every two hours (and after swimming).
#10: It’s good to get a base tan to prevent sunburn.
False.
According to the MD Anderson Cancer Center, a base tan – lightly tanning the skin before prolonged sun exposure — is equivalent to wearing sunscreen with an SPF of 3. This can create a false sense of security — leading people to spend longer periods of time in the sun, and increasing the likelihood of sunburn. Tanning causes skin damage, raises the risk of skin cancer, and should be avoided.
Dr. Mary Jenkins, a contributor to the Herald and member of its board of directors, retired after nearly 40 years as a family practice physician in New York state.