You’re not imagining it. When you slip your shoes back on after a flight, they really are tighter. That's because it's extremely common for feet and ankles to swell when you fly. It’s also usually harmless.

The fact is, you’ve just been sitting too long, and all the liquids in your body have sunk to your feet. The effect should only last a short time, and dissipate shortly after you walk off the plane. But there are things you can do to prevent swelling in the first place.

Exercise More

People who exercise often are generally less likely to be affected by gravitational oedema (the technical name for this phenomenon).

Avoid Salty Foods

Try and avoid salty foods before and during your air travel. This means staying away from the peanuts and other salty snacks, which can cause you to retain water and increase the swelling.

Get Loose

Try to constrict yourself as little as possible while you’re in the air. So no tight shoes, no tight-fitting clothes and no crossing your legs while you’re in your seat. The more you avoid these things, the better your circulation will be and the less likely you’ll be to get swollen feet.

Hydrate

Making sure you stay hydrated is the best way to keep your circulation from getting slow. Though it seems counterintuitive, getting enough fluids actually helps reduce swelling. Because when your body isn't hydrated enough, it holds onto the fluid it does have.

Consider Compression Socks

Compression socks (or compression stockings) are socks of various lengths that are designed to gently squeeze legs a bit more than typical socks. This helps promote better blood circulation in the legs. Swelling that doesn’t go down after a few hours after the flight and the resumption of normal activity may be due to something more serious, such as a blood clot (also known as deep vein thrombosis). Other signs of this condition include swelling that occurs only in one leg, or is accompanied by leg pain or shortness of breath. Seek immediate medical attention if you experience any of these symptoms.