Pollen is also an important source of airborne allergens, mainly from three major groups of plants: trees, forbs (i.e., graminaceous plants) and weeds, which are wind-borne pollinated flowers with diameters ranging from 10 μm to 100 μm. These pollens are unscented, light-colored, and numerous, producing flower grains that can release up to several million pollen grains, and the pollen in the air exists for periods ranging from a few hours to 4 to 5 days. The weight is also lighter, some have air sacs, the spread area is very wide, a few airborne pollen particles in the deposition before the wind can even be drifted to 14,000 meters or even 200 kilometers away, is the main pollen induced allergies. However, the farther away from the pollen source, the less airborne the pollen is and the less severe the triggering symptoms. The amount of pollen dispersed at different times of the day is related to air temperature, humidity, wind speed and direction. Rainy days can cause a sudden decrease in pollen grains. Pollen has a long pollen dispersal period, some of which can last for months. Pollen allergies are characterized by locality and seasonality. The concentration of pollen is higher in the air near plant growth. With the increase of international contacts, the territoriality of pollen is less obvious, but the seasonality is still obvious. According to pollen season can be divided into spring pollen, late spring and early summer pollen, late summer and early fall pollen. Due to the vastness of our country, the plant species are not the same everywhere, such as: 1, spring pollen: the north to plant cypress, pine, poplar, willow, elm, acacia and birch, while the south to wood hemlock, safflower goat’s foot, neem and sycamore, etc.; the south from February to April is the peak of the flowering of many trees, and the north is from April to June. Spring tree pollen in the air wafted for a very short time, thus causing the symptoms are generally mild, and the duration is also short, about more than ten days. 2.Late spring and early summer pollen: mainly pasture grasses, the flowering season is mostly from May to August. 3, late summer and early fall pollen: belongs to the weed class, weed class is an important source of worldwide allergenic pollen, our country to artemisia pollen as the main airborne allergens, followed by humulus, commonly known as Lara Yang, and other weeds such as quinoa, in the United States is mainly ragweed pollen. These grass pollens are airborne for longer periods of time. Overall, 90% of hay fever is due to summer and fall pollen. The peak airborne time for Artemisia pollen is June through October. The first and foremost measure to prevent pollen sensitization is to avoid or minimize exposure to pollen. Include the following measures: 1. Move temporarily or permanently during the pollen dispersal season; 2. Live in a room where pollen particles are filtered out during the pollen dispersal season, e.g., close the windows and doors in dry, hot or windy weather; 3. Avoid playing in parks during the pollen dispersal season; 4. Wear a face mask when you need to be outdoors during the peak season and use air conditioning appropriately when indoors; 5. In the above measures, move temporarily to a place where there is no or less pollen sensitizing air pollution. Among the above measures, the precautionary measure of temporarily moving to areas with no or less allergenic pollen during the pollen dispersal season is the most desirable, but it is difficult to implement.