Predisposing Factors Patients allergic to dust mites may experience rapid onset of symptoms when making their beds, cleaning their rooms, and when entering damp, old buildings, and improve outdoors, especially in dry environments. Does the condition worsen with exposure to pets? The absence of pets in the home does not exclude allergy to pets. Seasonal hay fever, the onset of which varies according to geographic location. Food allergies and intolerances are common in children to eggs, milk and peanuts; in adults to fish, shellfish, fruits, peanuts and other nuts. Often multiple tissues and organs are involved, e.g., stinging lips, angioneurotic edema, urticaria, eczema, nausea and vomiting. Physical Examination Skin The urticaria is an irregular, protruding epidermal eruption, often red at the base, and may be accompanied by subcutaneous angioneurotic edema. The urticaria may fuse into patches with marked itching that lasts for several hours (usually less than 24 hours). The presence of vasculitis should be noted if the urticaria-like rash is fixed and persists for more than 24-48 hours or leaves marks. A positive cutaneous scratch sign may accompany cutaneous urticaria or be present alone. The skin may be completely normal in the intervals between recurrent urticaria. The distribution of eczema is age-related. In infants and young children, eczema is mainly found on the head, face and trunk. Eczema in infancy and childhood is mainly distributed on the head, face and trunk. In older children, it is mainly distributed on the skin of the flexed sides of limbs. It is accompanied by more flaky skin after scratching, sometimes with blood oozing, which also suggests the presence of secondary infections. The skin is dry and thickened as a result of the chronic process. Nose The nasal appearance of allergic rhinitis may have transverse skin folds. Intranasal examination of the nasal cavity When symptomatic, the nasal mucosa may have the typical pale, bluish mucosal edema. Nasal congestion due to structural abnormalities of the nasal cavity should be excluded. Patients who inhale glucocorticoids may have Candida infections of the oropharynx. Laboratory Tests Routine Laboratory Tests Routine blood tests: eosinophil and basophil counts can be used as an adjunct to anaphylactic reactions. Attention should be paid to the distinction between parasitic infections and eosinophilic patients. Total IgE Serum total IgE levels are approximately 10,000 times lower than IgG and therefore require sensitive methods of detection. The concentration of IgE in cord blood is about 1 ng/ml, increasing with age to about 200 ng/ml Increased levels of IgE in cord blood have been reported to be associated with the development of allergic disease later in life, but this is debated. Parasitic infections have increased IgE. About half of patients with allergic diseases have total serum IgE at normal levels. Determination of allergens Skin tests The main skin test method currently used in China is the skin prick test. In addition, there are intradermal tests and skin patch tests. Skin prick tests are generally more sensitive than in vitro tests for allergen-specific IgE. However, it is required that the reagents used should be standardized and that differences between production lots should be avoided. In addition to their diagnostic benefits, skin tests are also of educational interest. The patch test is mainly used to diagnose delayed reactions. Allergen-specific IgE test Determination of serum allergen-specific IgE is mainly done by radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), chemiluminescence and other experiments. The earliest and most classical experimental method is the radioallergen adsorption test (RAST). The test is performed by adsorbing an allergen onto a solid-phase carrier and adding a certain amount of patient serum, which will bind to the allergen if the adsorbed allergen-specific IgE is present in the serum. Radiolabeled anti-IgE antibodies are added. ELISA is to change the anti-IgE antibody to enzyme labeling, add enzyme action substrate and then develop the color. The purity of allergens and detection conditions determine the sensitivity and specificity of the experiment. At present, China mainly uses skin prick test and ELISA to detect allergens. Histamine release from basophils Screening for allergic diseases can also be done by detecting histamine release from basophils caused by allergens. Its sensitivity and specificity are similar to RAST. TREATMENT Treatment of allergic diseases consists of three areas environmental control, medication and immunotherapy. Environmental control Environmental control is the first step in the treatment of any allergic disease. Environmental control is commonly known as allergen avoidance. In China, not enough attention has been paid to environmental control in the treatment of allergic diseases caused by inhalant allergens, and there is a lack of related products. Since the primary condition for the occurrence of allergy is the presence of allergens, effective control of the human body’s contact with allergens will have an effect on the sensitization and sensitization of allergic diseases. Environmental control is not only beneficial for treatment but also for prevention of allergic diseases. Methods of allergen avoidance vary according to the type of allergen. Broadly speaking, the absence of penicillin in patients with penicillin allergy is also a form of environmental control. Currently the most effective treatment for patients with food allergies is to avoid the food causing the allergy. Among the avoidance measures for various allergens, those for mites are better developed and studied. Although it is not yet possible to completely remove mites from the living room, the amount of mites can be significantly reduced by existing methods and measures that can significantly reduce the severity of the onset of mite allergy, the number of episodes, and the dosage of prophylactic medication. Environmental control measures for mites are related to the habits and biology of the mites. Warm, humid, dark environment is conducive to the breeding of mites, so the environmental control of the indoor environment emphasizes dry, ventilated, clean, man-made fiber cotton is not conducive to the growth of mites. 55oC above the temperature can kill mites. Cold and highland areas are not conducive to mite growth and reproduction. A more effective method is to use special dense fabrics made of sets, sets on pillows, bedding and mattresses to avoid mites and their excretions and human dander through, which can effectively prevent mites and their excretions from being inhaled by the human body and inhibit the growth and reproduction of mites. Antihistamines There are more than a dozen types of antihistamine drugs available in the clinic. It is best to familiarize yourself with the effects, dosages and side effects of three to four antihistamines. Side effects of antihistamines such as drowsiness often disappear with regular use. If tolerance to one antihistamine occurs, switching to another type of medication can overcome the tolerance. Antihistamines do not control all allergic diseases. A few years ago it was thought to be due to insufficient local concentrations of H1 blockers. Now it is believed that other biologically active mediators produced by inflammation in allergic diseases are responsible for this phenomenon. Histamine receptor antagonists can be categorized into different groups based on their structure, pharmacokinetics, pharmacodynamics and clinical use. The first generation of H1 receptor antagonists have a different chemical structure than histamine. While histamine consists of an imidazole heterocycle connected to ethylamine, H1 receptor antagonists consist of two heterocycles, or fenugreek rings, connected to one other atomic subunit (nitrogen, oxygen, or carbon). The atoms attached are important in structurally distinguishing the different agents. Moreover, the number of hydrocarbon groups and the heterocycles determine their lipophilic properties. Generally these drugs are rapidly absorbed after administration by mouth or intravenously. peak plasma concentrations are reached in 2-3 hours and systemic effects are seen in 30 minutes. Clearance is slow and widely distributed. They are mainly metabolized by the cytochrome p450 system in the liver through hydroxylation. In most patients the drug is excreted in an inactive form by urinary secretion within 24 hours. Plasma half-life is longer in adults than in pediatrics. Being lipophilic, they can cross the placental and blood-brain barriers. This can enter the nervous system producing side effects such as drowsiness. They can also be secreted through the mammary glands. First generation histamine antagonists and histamine binding to histamine receptors is competitively inhibited and can be reversed. Therefore the effect is highly dependent on the plasma concentration of the drug. When these drugs are metabolized to an inactive form and excreted in the urine, histamine receptors can bind to their surrounding histamine. This mechanism requires that the patient be medicated frequently to achieve optimal results. Prior to pharmacokinetic data, it was thought that the short half-life of first-generation H1 receptor antagonists required frequent dosing to achieve effect. Since the plasma half-life of drugs such as paracetamol is greater than 20 hours in adults, one or two doses per day may achieve the same effect. Extended-release agents also allow shorter half-life drugs to be administered less frequently, thus improving patient tolerance and reducing side effects. Because the new non-drowsy second-generation antihistamines do not structurally belong to the same class as the first generation, they have been categorized into different classes. Their structural and pharmacokinetic characteristics dictate that they have mild side effects and are easily tolerated by patients. Terfenadine (terfenadine, Mindy 60mg bid), astemizole (astemizole, restamine 10mg qd), loratadine (loratadine, kelentan 10mg qd), and cetirizine hydrochloride (cetirizine hydrochloride, cetrimide 10mg qd) are easily absorbed through the gastrointestinal tract. gastrointestinal tract. Plasma concentrations peak within 1-2 hours after oral administration. After absorption it is metabolized in the liver. Astemizole produces different metabolites by oxidative dealkylation via the p450-CYP3A4 pathway and fenvalerate ring hydroxylation. Most (>=60%) of the metabolites of terfenadine, astemizole are excreted in the feces and bile. Most fexofenadine does not require metabolism and is excreted via secretion into the feces and urine. Although the half-life of pediatric terfenadine is only 2 hours, the pharmacodynamics are the same as in adults. Loratadine is also metabolized in the liver by the p450-CYP3A4 pathway to produce the active metabolite descarboethoxyloratadine, which, unlike terfenadine and astemizole, is also metabolized by the isoenzyme CYP2D6. This altered pathway prevents the accumulation of the drug in the body in the presence of hepatic disease or when concomitant use of drugs with microsomal oxidase inhibitory effects results in inhibition of the p450-CYP3A4 pathway. Cetirizine is primarily secreted into the urine and is 50% unaltered. Metabolism in the liver is not important and it is used with caution in renal impairment. Pharmacodynamics In contrast to the first generation, second-generation drugs are not monocompetitive inhibitors. These drugs bind and detach slowly to H1 receptors in a noncompetitive manner. High concentrations of histamine do not displace their binding to histamine receptors. They are potential inhibitors of the Wheal-and-flare (WF) reaction. Their lipophobic nature prevents them from crossing the blood-brain barrier, so their effect on H1 receptors is only in the peripheral nervous system. They have low affinity for non-H1 receptors. Pharmacy Second-generation antihistamines are available only in oral formulations. They are dosed 1 or 2 times daily. A single dose (120 mg) of terfenadine has the same effect as 60 mg twice daily in improving symptom scores in allergic rhinitis and suppressing histamine-induced reactions. Astemizole and loratadine should be administered on an empty stomach to avoid absorption difficulties. Food has little effect on terfenadine, fexofenadine, and cetirizine. Second-generation antihistamines have fewer adverse drug reactions, and with the widespread use of second-generation antihistamines, some adverse reactions have been reported clinically. Among them, the risk of cardiotoxic reactions induced by astemizole and terfenadine is relatively high. Cardiotoxic reactions are mainly characterized by arrhythmia, Q-T interval prolongation, etc. A very small number of patients may experience syncope, which may lead to death in severe cases. However, overall such adverse reactions are rare, and are more uncommon in children than in adults. In addition, astemizole may be associated with increased appetite and weight gain. Glucocorticoids are widely used clinically. The systemic use of glucocorticoids in allergic disease is primarily for patients with severe, acute and potentially life-threatening conditions, including severe asthma, anaphylaxis and exfoliative dermatitis; self-limiting allergic reactions that are not life-threatening but have severe symptoms, such as severe contact dermatitis, serosurgeon’s reaction, or severe seasonal rhinitis and asthma; and chronic allergic disease in which conventional treatments are ineffective for short-term relief of symptoms. Topical and inhalation administration will be addressed in the context of each relevant disease. Leukotriene antagonists Leukotriene antagonists (e.g., cisplatin, etc.) have been marketed in recent years due to the important role that leukotrienes play in inflammation in allergic diseases, especially in delayed phase reactions. Other treatments Anti-IgE therapy has been used in the clinic. Currently it is mainly used in the treatment of asthma with efficacy. Immunotherapy Immunotherapy (IT) is also known as desensitization therapy in China. Immunotherapy is actually different from desensitization therapy, which is a short-term injection of antigenic substances to reduce the response of effector cells. Immunotherapy involves repeated subcutaneous injections of gradually increasing doses of allergens to alter the IgE-mediated immune response of allergic patients and to reduce or mitigate morbidity. The mechanisms of immunotherapy are complex and many of the components are still unclear. At present, this therapy is very effective for seasonal allergic rhinitis, insect toxin allergy; asthma is next to effective; and food allergy, eczema is not effective. In recent years, it has also been found that the administration of drugs through the gastrointestinal tract, sublingual and nasal mucosa can also achieve a certain effect, and the relevant clinical research is in progress. The exact mechanism of immunotherapy is not very clear. It can cause many changes in the body’s immune response, including the production of blocking antibodies (IgG antibodies) against allergens, reducing IgE antibodies, decreasing the sensitivity of mast cells and basophils to histamine release caused by allergens, and regulating the response of T cells.