Why allergies
We are familiar with allergies, but we may not know how allergies occur. Allergy is a series of hypersensitivity reactions caused by the human body after contact with some of the causes of allergies that have little impact on the average person in the environment.
Under normal circumstances, when foreign substances enter the human body, most of them face two fates, if recognized by the body as useful or harmless substances, these substances will live in harmony with the human body, and will eventually be absorbed, used or naturally excreted.
If these substances are recognized as harmful substances, the body's immune system immediately responds to drive them away or eliminate them, which 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 is beyond the normal range, that is, when the immune system attacks harmless substances, this situation is called an allergic reaction. The allergic reaction is not a psychopath, but the function of the body's immune system is "perverted", and allergies are a typical allergic reaction.
We often say that allergies mainly include type I and type IV hypersensitivity reactions. Although the two have different manifestations due to different pathogenesis, they have a certain genetic basis.
Type I hypersensitivity reaction
Type I hypersensitivity reaction is a rapid allergic reaction, generally after contact with the allergen can appear within a few minutes to several hours, the skin is manifested as urticaria, the respiratory tract is manifested by sneezing, a large amount of runny nose, shortness of breath, the eyes are manifested as conjunctival flushing, a large number of tears, gastrointestinal manifestations as abdominal pain, diarrhea and so on.
Type I hypersensitivity reaction, when the body is first exposed to allergens, the body does not immediately have an allergic reaction, but is first sensitized. This sensitization process is that after a certain allergen enters the body, it first induces B cells to produce specific IgE, which is a marker produced exclusively by B cells for this allergen, and then IgE will combine with the receptors on the surface of mast cells and basophils, so that the body is sensitized by this allergen, and the simple understanding is that this allergen is labeled on the body's cells. When the body encounters this allergen again, the allergen can directly bind to the previously made label IgE, so that mast cells and basophils are activated, releasing a large amount of histamine and inflammatory mediators, which cause blood vessels to dilate and congestion, and the plasma inside the blood vessels leaks into the tissues and stimulates the nerves.
Type IV hypersensitivity reaction
Type IV hypersensitivity is a delayed allergic reaction, which generally occurs gradually after 24-72 hours of contact with the allergen, and is mainly manifested by eczema dermatitis on the skin.
Type IV hypersensitivity reaction and type I hypersensitivity reaction is the same, IV hypersensitivity reaction also has a sensitization process, when a certain allergen first enters the body, the body's antigen presentation cells are taken up and processed, and then placed on the surface of the cell membrane quietly waiting for the person to claim, and the person with the relationship is the T cell with a specific antigen receptor, when the processed allergen and the specific T cell recognize and combine, the T cells are sensitized. If the body is exposed to this allergen again, the sensitized T cells will be activated, releasing a large number of cytokines, which cause inflammatory reactions and tissue damage, the most intuitive manifestation of which is the appearance of dermatitis eczema.
Skin sensitivity = allergies?
Because allergies include two different manifestations of type I and type IV hypersensitivity reactions, the mechanism by which they occur is also different. However, in daily life, many people think that many situations that are not allergic are allergies, which leads to blind panic and deviations in treatment, so it is necessary to identify them.
It can be seen from the foregoing that the pathogenesis of allergies has two characteristics: one is the participation of the organism's immune system, and the other is specific. Skin sensitivity is based on the destruction of the skin barrier, or the skin's tolerance to poor and non-specificity due to trauma, inflammation and other stimuli. In addition to the skin, this distinction also exists in the respiratory tract, digestive tract and other organs, corresponding to different diseases, treatment methods and treatment principles are different.
Allergies For people with their own atopic constitutions, allergies are indispensable for them to hide and must be faced. If allergies develop, we should deal with them methodically, and treatment of allergies includes avoiding known allergens and using corticosteroids and antihistamines. In case of severe allergies, intravenous epinephrine should be given urgently. The so-called Allergen immunotherapy is a treatment that gradually exposes patients to an increasing number of allergens, and is often used for specific allergic diseases, such as hay fever or insect bites.
In addition, for these allergic diseases, you should find a doctor in the corresponding department, such as otolaryngology, respiratory medicine, if the patient is a child, then find a doctor who is good at allergic diseases in pediatrics for long-term comprehensive treatment and management.
Popular science content can not replace the doctor's diagnosis and treatment opinions, for reference only; the specific use of drugs need to be used under the guidance of professional doctors!
The End
References: MSD Manual, Wikipedia, Baidu Encyclopedia
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