Sleeping is probably the most common activity while on an airplane. What else is there to do? You can't go anywhere and there's no wi-fi unless you want to pay some exorbitant fee. So sleeping is one of the few options travelers have. But according to medical experts, you shouldn't be sleeping your entire flight.

Several doctors have recently come out and said that airplane passengers should not sleep during takeoff or landing during their flights. The body undergoes drastic altitude changes during these moments, and sleeping during those times does not allow the body to deal with those changes adequately.

"A quick change in altitude affects the air pressure in the ear. This leads to a vacuum in the Eustachian tubes which makes the ears feel blocked and sound dull," says British pharmacist Angela Chalmers. "Try not to sleep during takeoff and descent as you will not be swallowing as frequently and this can lead to blocked ears."

The website MedlinePlus, which is run by the U.S. National Library of Medicine, says sleeping on planes can cause "ear barotrauma," because your body isn't allowing air to flow in and out of the middle ear. They say, "Swallowing or yawning opens the Eustachian tube and allows air to flow into or out of the middle ear. This helps equalize pressure on either side of the ear drum. If the Eustachian tube is blocked, the air pressure in the middle ear is different than the pressure on the outside of the eardrum. This can cause barotrauma."

So next time you go flying, you might want to re-consider taking that sleeping pill.