We’ve all seen it. Someone you know comes back from a vacation sick because they were on a plane. Re-circulated air is one culprit. Dry air and the body’s response to a lack of humidity is another.

We can’t always avoid flying, so there are ways to reduce the risk of catching something while on a plane.

1. Hydrate – Most commercial planes fly at higher than 30,000 feet, which means the humidity is well below the 15 percent required to keep nasal passages moist. When the mucus membranes of the nose and throat get dry, it inhibits the natural drainage system that carries any viruses or bacteria encountered down to the stomach to be flushed out. Drinking water keeps the mucus membranes in the nose and throat moist and better equipped to fight germs.

2. Protect your nose – Use a saline nasal solution or nasal mist to keep your nasal passages moist (just follow the directions on the bottle), which effectively boosts your body’s own germ-flushing action. The steam from hot drinks is another option.

3. Bring your own snacks. In 2010 the FDA issued a warning about food-borne illness from airplane food, reporting that cockroaches, ants, flies, and debris had been found during flight inspections. The FDA also detected the deadly bacteria listeria in samples taken from a kitchen floor.

4. Stay away from sick people – OK, this one is easier said than done. But not impossible. If you think someone close to your row is a germ dispenser, ask if you can move. You can either be truthful about the situation or try another tactic, such as volunteering to be in an exit row, asking to be closer to the bathroom, or offering to switch places with someone who wants to sit closer to children or other family members. If you can’t move, keep your seat forward. Sometimes a few inches can make all the difference. Bringing a face mask is another idea. It might look funny, but better that than getting sick.

5. Pack disinfectant wipes, and use them to wipe down tray tables, seat arms, remote control devices, and TV touch screens. Use alcohol-based hand sanitizers, wash your hands regularly and avoid touching your face.

6. Check with the airline to see if filters the re-circulated air. Don’t be afraid to use the blower vent above you. The air might be a little cold, but the blowing action can send germs in the opposite direction from your face.