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Besides your passport and boarding pass, there's one more item that travel bloggers (and doctors, for that matter) highly recommend you always have with you on a flight.

It's not a sanitizer, despite recent stories of germ-laden airport and airplane fixtures: Rather, it's a moisturizer called Cetaphil, available at drugstores for about $3.

Many people have their own preferred moisturizers packed in their luggage, but experts say you should also buy a good, travel-sized moisturizer to apply (and keep reapplying) on board.

The reason: Flights will dry out your skin faster than a desert, according to Los Angeles dermatologist Aegean H. Chan. While she advises drinking water before and during a flight, she cautions that's not enough to save your skin from an airplane's ultra-dry atmosphere.

Consequences of the low humidity — often just 10% or 20%, Chan says — can include discomfort, inflammation, cracking or flaking.

Some travel bloggers even advise taking your moisturizing ritual one step further. Nicole Andersson suggests applying Vaseline, serums (packed in TSA-approved sizes) and Korean face masks in flight.

But the simplest (and most affordable) option is to keep a small bottle (less than 3 ounces) of Cetaphil moisturizing cream in your carry-on luggage.

"I try to be as prepared as I can be," says frequent traveler Andersson.

A travel-size, 2-ounce Cetaphil moisturizer bottle costs $2.99 at Target.