Pollen allergy is a type I allergic disease induced by allergenic pollen, and is a common clinical disease. Allergic rhinitis, allergic conjunctivitis, allergic cough and asthma, and skin allergy induced by pollen are commonly referred to as hay fever, of which allergic rhinitis is one of the main symptoms of hay fever, and because its onset is closely related to the pollen season, it is sometimes referred to as seasonal allergic rhinitis. I. The main types of allergenic pollen in China There are many types of allergenic pollen in the atmosphere, and as many as hundreds of plant pollens are known to cause human allergy. Different countries, different regions, different altitudes and different seasons can have different allergenic pollens. As China’s north and south span the temperate and subtropical zones, coupled with the large east-west span, there are large regional differences in allergenic pollen species. Subtropical plants dominate in Guangdong, Guangxi and Hainan, temperate plants dominate in the Yangtze River basin and East China, and hardy plants dominate in Northeast, Northwest and North China. In most areas of China, there are two peak periods for the dispersal of pollen in the air during the year, the first peak is in spring, dominated by tree pollen, which is predominant from February to May depending on the region, and the second peak is dominated by grass pollen, which is from July to November. In the north of China, for clinical importance, Artemisia pollen is the most critical species causing pollen allergy, followed by ragweed, grass and grass pollen. In the south, pollen of Artemisia, Gramineae and Quinoa are predominant. Clinical symptoms Patients with hay fever usually have atopic qualities, so attention should be paid to the allergy history of family members (including allergic rhinitis, asthma and allergic skin disease) and personal allergy history (such as eczema in infants and children), which are important to assist in the diagnosis. When pollen is inhaled into the respiratory tract, it is first deposited in the upper respiratory tract and can invade the lower respiratory tract when higher concentrations of pollen are inhaled. After deposition in the nasal mucosa, the secretions of the mucosa leach out the allergen molecules from the pollen and bind to the antigen-presenting cells through the mucosal barrier, thus leading to a series of allergic reactions. Therefore, patients usually first develop obvious upper respiratory symptoms, and most patients have upper respiratory allergy symptoms first, followed by other allergy symptoms such as itchy eyes, conjunctival congestion, cough, sputum and wheezing. 1. Signs and symptoms of upper respiratory tract allergy mainly include allergy of the nose or pharynx. Nasal symptoms include symptoms of allergic rhinitis associated with pollen season such as itchy nose, sneezing and runny nose, which may be accompanied by itchy eyes, ears and palate. Sneezing may occur several or even dozens at a time, and the sneezing episodes may be accompanied by large amounts of watery or clear mucus-like nasal discharge. Most patients may have alternating or persistent nasal congestion. Typical nasal signs are pale white, light gray or gray-blue nasal mucosa, mucosal edema, and watery or mucus-like secretions in the nasal passages. The above mentioned nasal symptoms and signs are obviously related to the seasons. The symptoms of the throat are mainly manifested as pharyngeal itching, foreign body sensation in the pharynx or itching in the soft palate area, and a few patients may have irritating cough due to secretions in the pharynx. 2. Lower respiratory tract allergy symptoms When inhaling higher concentrations of pollen, hay fever patients may also have lower respiratory tract allergy symptoms, such as coughing, wheezing and sputum. Some patients also have upper and lower respiratory symptoms at the same time or have lower respiratory symptoms first and then upper respiratory symptoms. 3. Other allergic symptoms include eye and skin allergy symptoms. Eye symptoms are symptoms of allergic conjunctivitis, including itchy eyes, tearing, redness of the conjunctiva and eyelids, etc., and allergic rhinitis can be collectively referred to as allergic rhinoconjunctivitis. Skin allergy is mostly manifested as skin papules or itching on the face, limbs and other exposed areas, and eczema-like changes can be seen in severe cases. 4. The characteristics of hay fever episodes The characteristics of hay fever episodes are mainly seasonal, regional and related to climate change. Seasonal attacks The onset of allergic symptoms coincides with the flowering period of plants, and attacks occur at a relatively fixed period every year, and the allergist in each region should master the flowering period and pollen dispersal characteristics of local allergenic plants in order to make a correct diagnosis for the patient. Seasonal attacks last for a few days or a few months, and remit naturally once the pollen dispersal period is over. Some hay fever patients who are allergic to room dust and dust mites may have perennial episodes with seasonal exacerbation. Patients usually develop hay fever only in areas where allergic pollen is dispersed, and their symptoms can be relieved quickly when they move to areas where pollen is not dispersed. Therefore, it is important to know the type and amount of pollen dispersed in the local atmosphere for diagnosis. Climate change can change the concentration of pollen in the air and thus affect the symptoms of hay fever, such as cloudy days during the rainy season, foggy season, rainy days and when there is no wind, the symptoms can improve naturally; when it is dry, hot and windy, the symptoms can intensify. The wind direction also has a great influence on the disease, for example, Qingdao city is south of the sea, so hay fever will be relieved when the south wind is blowing.