The next time your eyes water and breath labors, don't automatically blame the trees outside. It could be your air freshener or the food dye in your cereal. “Most household products aren't tested to see if they cause lung reactions or asthma,” says Kenneth D. Rosenman, MD, chief of the occupational and environmental medicine division at Michigan State University in East Lansing. “Furthermore, manufacturers aren't required to list any ingredients except disinfectants.” As a result, your home likely contains dozens of contaminants that can cause anything from itchy skin to asthma. Follow this expert advice on how to identify and avoid common allergy-inducing toxins.