I. What is allergic rhinitis
Allergic rhinitis, also known as allergic rhinitis, is a type I allergic inflammatory disease caused by the inhalation of external allergic antigens in patients with allergies, which occurs mainly in the nasal mucosa and is characterized by sudden nasal itching, sneezing, runny nose, nasal congestion and other major symptoms, and recurrent attacks, mainly mediated by IgE antibodies. It is classified into intermittent and persistent according to the duration of symptoms, and mild and moderate-severe according to whether it affects the quality of life. With the development of industrialization, the causative factors of allergic rhinitis are increasing and the incidence is rising year by year. In Western countries, the prevalence of allergic rhinitis is generally 10%-20% in adults, and up to 36% in northern China.
Second, what are the common causes
(i) Genetic factors
There is a family history of allergic reactions susceptible to this disease. The patient’s family has a history of asthma, urticaria, allergic conjunctivitis or drug allergy. In the past, these patients were called atopic individuals (allergic), and their IgE antibodies were higher than normal people. Three conditions must be present for an allergic reaction: the allergen, the atopic individual, and the meeting of the allergen with the atopic individual. Certain antigenic substances, which are harmless to most normal individuals, develop once they act on an atopic individual.
(ii) Nasal mucosal susceptibility
Susceptibility arises due to frequent stimulation by antigenic substances, but the degree of susceptibility varies depending on the number of mast cells and basophils in the nasal mucosal tissue and the ability to release chemical mediators. It has been shown that in the nasal mucosa of patients with allergic rhinitis, the number of these cells is not only higher than normal, but also has a stronger ability to release chemical mediators.
(iii) Antigenic substances
Antigenic substances that can stimulate the body to produce IgE antibodies are called allergens (also called allergens) and are necessary for the occurrence of allergic reactions. There are 2,000-3,000 common antigenic substances and nearly 20,000 medically documented ones. When the allergen substance re-enters the nasal mucosa, it binds with the corresponding IgE, causing the release of chemical mediators from mast cells and causing a metamorphic reaction. The allergens that cause this disease are divided into inhalation, ingestion, injection, contact and other types according to the way they enter the body, and inhalation and ingestion allergens are common. Common allergens are.
1, inhalation allergens
Inhalation through breathing into the nasal cavity. These allergens are mostly particulate matter suspended in the air.
(1) Pollen: Not all pollen from plants can cause disease. Only those pollens with high pollen volume, extensive vegetation, strong allergenicity, and spread by wind are most likely to be allergens. Due to differences in vegetation species, pollen with allergenicity differs from region to region. For example, in Northern Europe, pollen from birch trees and timothy grasses are dominant; in North America, ragweed is dominant; in Japan, pollen from cedar trees is dominant. China’s vast territory, allergic pollen is not consistent from region to region, the northern region more in July-September episodes, wild artemisia pollen is the main, but in the north and south of the river are found ragweed, should pay attention to. In recent years, it is believed that with the continuous development of industrialization, the concentration of harmful substances such as sulfur dioxide in the air increases, which can cause the protein structure of pollen suspended in the air to mutate, so that the original pollen without allergenicity, also has a strong allergenicity. This may be one of the main reasons for the significant increase in incidence. The pollen type and content in the air have significant seasonality and dispersion period, and the peak of pollen dispersion is in spring and summer and autumn.
(2) Fungi: Extremely widely distributed in nature, mainly found in soil and decaying organic matter. Its mycelium and spores are allergenic, but the spores are stronger. Spores can be widely spread by wind, and the number in the air is sometimes higher than pollen, and higher in rural than urban areas. The most common species of fungi is the genus Monospora, Streptomyces, Penicillium, Aspergillus and Saccharomyces. Among them, the single-spore mycorrhizal fungi and cross-streptomycetes have significant seasonality, the peak number of its spores in the air more in the summer. Indoor high temperature and dark and humid, are conducive to the growth of fungi. Indoor ornamental plant pots of soil, but also often become a good place for fungi to grow.
(3) Mites: There are hundreds of species, and there are five common domestic dust mites, of which dust mites and house dust mites are most likely to cause allergic rhinitis. Recently the tropical five-clawed mite has attracted attention, but the general dust mite test does not include it. If the test results show no response from dust mites, be aware of the possibility of the tropical five-clawed mite. It belongs to the arthropod phylum Arachnida. Adult mites are generally 300-500 microns in size, very small and invisible to the naked eye. They are mainly found in all corners of the house, most often in mattresses, pillows, carpets, sofa cushions, clothes, and toys with hair. It feeds on the dander, nails and hair shed by people or animals. It reproduces the most in late summer and early autumn. Mites’ excrement, eggs, debris and their disintegrated limbs can all be allergens.
(4) Animal dander: Animal dander is one of the strongest allergens. Susceptible individuals can be sensitized if they have prolonged contact with the animal in question. If re-exposed after sensitization, even a small amount of dander can stimulate allergic symptoms in the nose. Animal dander that causes respiratory allergic reactions comes mainly from animals in close contact with people, such as domestic pets (ornamental dogs and cats), domestic dogs, cattle, horses and sheep.
(5) Feathers: feathers from poultry or bedding, pillows, clothing, and feathers shed by domestic ornamental birds can be allergens. Closely related to house dust mites.
(6) Insects: such as cockroaches, mosquitoes, flies, moths and other dander, secretions, excretions, etc., can also be sensitizing.
(7) House dust: refers to the stale dust in the house, which is one of the common allergens causing perennial rhinitis. Its composition is quite complex and is a hodgepodge of various substances, including a combination of animal, plant and chemical substances.
(7) Other: such as willow, paint, oil smoke, car exhaust, gas, cigarettes, etc.
2.Eating allergens
It refers to allergens that enter the body from the digestive tract and cause nasal symptoms. The way it acts on the nasal mucosa is very complex and still not very clear. Milk, eggs, fish and shrimp, meat, seafood, animal fat, allogeneic proteins, alcohol, drugs, antibiotics, anti-inflammatory drugs, sesame oil, onion, ginger, garlic, a certain shoe vegetables, fruits, etc., can become allergens.
3.Injectable allergens
Such as antibiotics, xenogeneic serum, etc.
4.Contact allergens
Such as cold, hot air, ultraviolet light, radiation, cosmetics, shampoo, detergent, hair dye, soap, chemical fiber products, plastic, metal jewelry (watches, necklaces, rings, earrings), bacteria, mold, viruses, parasites, etc.
5.Self-tissue antigens
Mental stress, work stress, microbial infection, ionizing radiation, burns and other biological and physical and chemical factors, and the structure and tissue changes of their own tissue antigens. As well as due to trauma or infection and the release of their own hidden antigens, can also become allergens.