Onboard ailment: Ears popping / partial hearing loss Why it happens: Changes in altitude alter the pressure in your ears, which can cause discomfort and even temporary hearing loss. How to avoid it: There's no 100% way of avoiding this annoying condition, but regularly swallowing can make a difference as it helps the flow of air. Therefore it's wise to stay awake during descent (when problems usually arise), and suck on a sweet or chew gum. "Airplane ear" is more annoying if you fly when you have a cold, so if you're under the weather, get tanked up on decongestant medicines and nasal sprays before you travel (always reading the label first, of course).
If you don't get your hearing back fully upon landing, don't panic - it may take a day or two before you can hear normally again. But if symptoms persist, visit a doctor.