Believe it or not, you don’t need to climb to the top of Mount Everest or ski the highest mountain to get altitude sickness.

It may surprise you to learn that you can feel the effects at much lower elevations.

And it can happen when or where you least expect it. We’re talking cities like Denver, Santa Fe, and Laramie, Wyoming.

You see, altitude sickness is the body’s reaction to changes in oxygen and air pressure.

Symptoms include headaches and shortness of breath, both of which are easily ignored and potentially dangerous. These can progress into more serious problems such as fluid in the lungs.

So as soon as you get off the plane give your body time to adjust and don’t push yourself too far, or too fast.

Stay hydrated and eat. The higher you get, the more your body needs water and energy, and the more your appetite and thirst will decrease. This is especially true when you’re exert yourself with an activity like skiing or hiking.

If you start to feel sick, get yourself to a lower altitude and the symptoms should subside.

The smartest move: Continue to hydrate yourself. And that doesn’t mean having a few drinks at the lodge—at least not on your first day!

Get more tips on staying healthy when you travel in our Travel Health & Fitness section.

And check out the rest of our Daily Travel Tips here