Dust mites live in bedding, upholstery, and carpets. Cockroach body parts and waste products are also a major household allergen, especially in inner cities. Asthma rates of inner city children are high due to air pollution and also cockroach exposure in overcrowded buildings. Pollen is another important cause of allergies. Trees, weeds, and grasses release these tiny particles into the air to fertilize other plants.
Most people know pollen allergy as hay fever or rose fever.
Pollen allergies are seasonal, and the type of pollen a child is allergic to determines when he will be symptomatic. For example, in the mid-Atlantic states, tree pollination begins in February and March, grass from April through June, and ragweed from August through October. Pollen counts measure how much pollen is in the air. Although they are not exact, the local weather report's pollen count can be helpful when planning outside activities. Molds are fungi that thrive both indoors and out in warm, moist environments.