If you suffer from year-round allergies to dust ones, Summer weather is not your friend. The air gets full of moisture, which dust mites love. Since those little buggers require 50 percent humidity in order to thrive, you want to figure out how much humidity is in your home (especially your bedroom), and make sure the humidity is under that magic number. In order to figure that out, you'll want to pick up a hygrometer ($14.99), a neat device that measures the amount of humidity in the air. If the humidity is above 50 percent, then you'll need a dehumidifier ($199). The opposite of a humidifier, these little machines pull water out of the air decreasing the humidity in the room. Drier air definitely makes allergy symptoms less severe.