Making your home inhospitable for allergens sounds like a daunting task. In a particulate sense, it’s going to be you against millions of mold spores, dust mites and pollen. Fortunately, though, you’re smarter than these minute microbes, and following these tips can help you keep allergies at bay. A well-ventilated house and nonleaking ductwork is a first line of defense against bringing allergens into your living space. Use HEPA (high-efficiency particulate air) filters in the air conditioning system. Maintain the humidity level in the house at about 50 percent. Mold likes moisture, and dust and pollen are easily stirred in dry air. Keep your windows closed when pollen counts are highest: in the early morning hours, between 10 a.m. and 3 p.m., and in windy conditions. Pollen and mold spores settle on clothing, so when you come in from outdoors, remove your outer garments in the mud room, and take a shower.