What is an Allergy?

Under normal circumstances, when foreign substances enter the human body, most of them face two destinies. If they are recognized as useful or harmless substances by the body, these substances will live in harmony with the human body, and will eventually be absorbed, used or discharged naturally. If these substances are identified as harmful substances, the body's immune system responds immediately and expels or destroys them. This is the protective effect of the immune response. Immune response is one of the important functions of the human defense system, but if this response goes beyond the normal range, that is, when the immune system attacks harmless substances, this situation is called an allergic reaction. Allergies are a disease, because an unprovoked attack can also damage normal body tissues, and even the immune system sometimes attacks and destroys the body's own tissues, which is very detrimental to human health.

• TA says

2018-03-26 11:03 Those that make you allergic may be poisonous2018-03-26 11:03

Itching, dyspnea, abdominal pain, diarrhea and even shock caused by allergies in life, but have you ever thought about what causes allergies? ... more

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Basic Information

English name

hypersensitivity

Visiting department

Allergy Section

Common causes

Food allergies, allergies, etc.

Common symptoms

Paroxysmal pruritus, congestive wind mass, or even shock

Causes of Allergies

The causes of allergies can be roughly divided into external and internal causes.

External cause

Certain substances can cause abnormal reactions in the immune system of some people after entering the body. These substances are called "allergens (also known as allergens)" and are the culprits of allergies. Allergens are mostly macromolecular substances, such as certain proteins or peptides. Common allergens (wheat, peanuts, soybeans, nuts, milk, eggs, fish, and crustaceans) are caused by food allergies. Allergic diseases account for about 90% of the total number of allergies), inhaled matter (pollen, house dust, mites, etc.), microorganisms (molds, bacteria, etc.) and insect toxins, drugs (such as penicillin, sulfa, etc.), xenogeneic serum and physical factors Wait. These substances can enter the body through ingestion, inhalation, contact and injection. Macromolecular substances are directly used as antigens, and small molecule substances (haptens) can be combined with certain substances in the body to form new antigens (allergens). Allergens can cause sensitization of the body after entering the body for the first time, and allergic reactions occur when these substances enter the body again. Stimulates the patient's immune system for abnormal activities, eventually causing a series of allergic injuries.

Internal cause

Not all people are allergic. In the same situation, some people are allergic and some people are not allergic. This fact tells us that allergy requires an internal cause. The internal cause is the "allergic constitution" of some people. Allergies refer to the deficiency of the immune system of certain groups of people. Their immune systems are different from ordinary people, so they are prone to make "unrecognized opponents and unreasonable attacks", leading to allergies. Patients with allergic diseases are mostly hereditary. If both parents have allergic diseases, 75% of their offspring are likely to develop allergic diseases, 50% of which occur in the first 5 years after birth, and increase with age. The incidence of allergies will gradually decrease.
In recent years, as the process of industrialization, urbanization, and globalization has accelerated, people's living rhythms and methods have continued to change, life and work pressures have continued to increase, and the variety of foods and processing techniques has increased, resulting in many original non-allergic The crowd may gradually evolve into people with allergies, which will continuously expand the potential allergic population. At the same time, with the improvement of technology and medical standards, many previously unrecognized allergies have also been revealed. This is the current occurrence and discovery of allergies More and more sake.

Allergic epidemiology

The incidence of allergies is high, and about one third of people have reported allergic diseases in their lives. According to statistics from Beijing, China, the incidence of allergies in the general population is about 15%. In some parts of the Pacific, allergic diseases are as high as 50%. Since the beginning of the 21st century, the disease has become one of the most common global diseases.

Allergic Common Allergic Diseases

Urticaria

It is an allergic skin manifestation, characterized by onset of skin itching and the appearance of congestive wind masses. Allergens (mostly foods and additives, inhalants, drugs, microorganisms and parasites, insect toxins, etc.) come into contact with patients' skin and mucous membranes and enter the body. It is clinically divided into two categories: one is non-specific immunoglobulin IgE-mediated type allergic urticaria, and the other is non-allergic urticaria, including physical, cold, fever, solar, and Cholinergic urticaria. In addition, physical, mental and systemic diseases can also cause urticaria. Other skin manifestations of allergies can also include angioedema, dermatitis, eczema, erythema polymorpha, and exfoliative dermatitis.

Clinical manifestations: Pink wind masses of various sizes suddenly appear on the skin, mostly round, oval or irregular, which can occur in any part of the body; isolated or scattered at first, and then gradually expanded and merged into a sheet. Urticaria often comes and goes quickly, one after another, and new wind masses will occur one after another, even on top of the old ones. Some patients may involve the gastrointestinal tract, causing edema of the mucosa in this area, and abdominal pain and diarrhea may occur clinically. Breathing may occur if mucous membranes of the throat are involved. Severe patients may be accompanied by palpitations, irritability, nausea and vomiting, dyspnea, edema of the throat, and even anaphylactic shock such as decreased blood pressure.

2. Allergic rhinitis

Most of them are the result of interactions between inhaled allergens and nasal mucosa of patients, and patients are mostly allergic and hereditary. Clinically, it can be divided into two types: seasonal rhinitis and perennial rhinitis. The former is caused by inhalation of pollen, while the latter is caused by inhalation of dust, mites, molds, animal hair, dander and poultry feathers.

Clinical manifestations: sudden nasal itching, continuous sneezing (more than 5), and a large amount of water-like serous nasal secretions. The symptoms last for more than 1 hour per episode, and often occur repeatedly.

3. Allergic shock

Is the most serious allergic reaction, the most common allergen leading to the disease is penicillin, other drugs such as lactam antibiotics, streptomycin, procaine, isatis injection, dextran, iodine-containing contrast agents, etc. There are also certain insect stings. The incidence of anaphylactic shock in the general population is about 0.08%. After the onset of the disease, extensive capillary permeability increased sharply, arterial dilation, decreased peripheral blood flow, decreased cardiac output, and decreased circulating blood volume. At the same time, it led to edema of multiple organs and multiple systems and spasm of smooth muscle. Severe cases can be fatal in a short period of time, and 20% of allergic deaths die within half an hour of an allergy.

Clinical manifestations: The patient first developed flushing of the skin and mucous membranes, itching all over the body, and itching in the palms was more obvious. The lips, tongue, and extremities had numbness, and then various rashes appeared, mostly windy masses, large dermis and subcutaneous blood vessels Edema. Blood pressure dropped sharply, systolic blood pressure dropped below 80mmHg, and pulse pressure was within 20mmHg. In severe cases, circulatory failure can occur, manifested as blurred consciousness, cold sweat, pale complexion, cold limbs, and pulse. If the condition is not controlled in time, a small number of cases may have cardiac arrest until death in a short time.

4. Hay fever

The disease, also known as hay fever, is caused by patients' allergies to plant pollen, mainly affecting the eyes and upper respiratory tract. Most of the disease is caused by pollen from the wind as a transmission medium as an allergen. The main pathogenic pollen in China is Pollen of the genus Polygonum, as well as pollen of sunflower, hemp, sycamore, castor, genus Polygonum, Cucurbita, poplar and elm. There are also a small number of patients who are caused by fungi, dust mites, or other seasonal inhalants or food.

Clinical manifestations: It has obvious seasonal and regional characteristics, mainly manifested as itchy eyes, tears, and eyelid redness; itchy nasal cavity and continuous sneezing, often up to a dozen at a time, and watery secretions increase after sneezing. Onset lasts all day long; itching, dry throat, dry cough and so on. Some patients can hear wheezing on auscultation.

5. Allergic asthma

The disease is the main type of bronchial asthma. It is an extensive airway hypersensitivity caused by allergens or other allergic factors. It causes airway obstruction syndrome characterized by airway reversibility and spastic stenosis. The disease mainly affects the bronchus. . The main causes of the outbreak are inhaled allergens (house dust, house dust mites and dust mites, as well as fungal spores, various plant pollen, animal dander, feathers, silk, old fabrics, insect limbs, Debris, feces, molting, worm eggs, etc.), food (such as some eggs, etc.), medicine (aspirin, etc.). Not all bronchial asthma is associated with allergies. Other types of bronchial asthma include: infectious asthma due to infection, physical asthma induced exercise asthma, mental asthma caused by mental factors; occupational asthma caused by occupational exposure to certain non-specific stimuli; and non-sensitization Asthma caused by factors such as cold air, menstruation, pregnancy, childbirth, etc.

Clinical manifestations: Many sudden attacks or exacerbations, paroxysmal expiratory dyspnea and wheezing, the general attack time is several hours. Before the onset, there are many signs of mucosal allergies such as sneezing, runny nose, cough, etc., followed by a sense of chest urgency, severe cyanosis, sweating, sitting posture, and loss of consciousness. Relief or spontaneous relief after using antiasthmatic drugs. When the symptoms are relieved, sticky foamy sputum can be coughed. The main signs seen on the physical examination are extensive wheezing when exhaling.