It might sound like common sense, but hear me out. Once the weather gets warm, I'm sure you'll be tempted to open up the windows and let the fresh air in — but beware. That fresh air is full of pollen, allergens, dander and everything that can cause an unwanted reaction. Keep the windows closed to keep those harmful irritants out. Another pro tip: Turn on your AC so the air circulates and prevents dust or allergens from settling.