Ah, it’s spring at last! But for some people, they’re not saying “ah”: They’re saying “achoo!” as allergy season kicks into high gear. At this time of year, there’s plenty of pollen in the air, but that’s not the only cause of people’s sneezes. In fact, one of the biggest sources of allergen exposure is probably right under your feet: your carpet. Rugs act like sponges, providing a comfy home for dust and dust mites, dander, pollen, and even mold.…