Red eyes and a stuffy nose at the office may not be due to a cold – and sometimes plants can be a big help. Some poorly ventilated offices are teeming with allergens and irritants, which are spread all too effectively by air conditioning systems. But there’s a cure for the problem. Medical researchers have long known that plants in the office or living room not only improve the mood but also clean the air. Formaldehyde, benzene, and ammonia are toxins for us, but they're a feast for weeping figs, Monstera, and chrysanthemums. Plants also insulate against noise and regulate humidity.