(CNN) — It'll be a while before it's warm enough for homeowners in some parts of the country to open their windows and let in fresh air. Here are some basic tips on what to do in the meantime.

It's the middle of winter and homes in Chicago are sealed up tightly. But that can create problems indoors.

As people spend more time inside, they're getting exposed to all the things that aren't circulating.

Allergist Kathleen Sheerin says stagnant air leads to a common form of indoor air pollution.

“For some people who aren't allergic, it can just make you stuffy and your eyes a little irritated," she said. "But if you're one of the 20 percent of the population who has allergies, it may actually cause the same reaction that you see at the height of spring."

Sheerin says pet dander, cigarette smoke and even particles from a fireplace can irritate delicate sinus passages.

She recommends doing some winter cleaning starting with the furnace.