What is an allergic reaction? An allergic reaction, also known as a metamorphosis, is an abnormal reaction of the body to one or more substances that are generally harmless to normal people. It is mainly caused by an excess of a special antibody called immunoglobulin E (IgE) in the body of the allergic person. It reacts with allergenic substances (allergens) in the environment and stimulates the body to release excessive amounts of chemicals, which in turn produce various allergic symptoms. What are the types of allergic reactions? There are 2 main types of allergic reactions. One is a rapid-onset reaction, such as penicillin allergy, which generally develops within 30 minutes of exposure to the allergen; the other is a delayed-onset reaction, which generally develops several hours to a week after exposure to the allergen. This late onset allergic reaction is easily ignored by the patient, who cannot remember what he or she was exposed to that caused the allergic reaction. Chronic allergy can develop when the body is exposed to an allergen for a long period of time. Are allergies and poisoning the same thing? Allergy and poisoning are not the same. Poisoning refers to the physical and chemical damage caused by certain toxic substances to the human body, and all people may react to toxic substances; allergy refers to the allergic reactions of some special people (allergic) caused by certain allergenic substances (generally common substances in life, not toxic). In short, poisoning is an abnormal reaction of ordinary people to special substances; allergic reaction is an abnormal reaction of people with special constitution to ordinary substances. Another difference between allergy and poisoning is that the degree of poisoning is directly proportional to the amount of exposure to harmful substances. The more harmful substances accumulate in the body, the more serious the poisoning is; whereas allergy is not related to the amount of exposure to allergens, but only to the number of exposures. Generally speaking, when the human body is exposed to an allergen for the first time, it usually does not develop the disease, but causes the body to form a sensitized state. Allergic reactions occur only when the body is exposed to the same allergen later. Who can have an allergic reaction? Anyone can have an allergic reaction, but if one or both parents are allergic, the likelihood of a child having an allergic reaction is greatly increased. The global prevalence of allergic diseases is 20%. Why does allergy suddenly occur in skin that is not originally allergic? 1. When the human body is exposed to an allergen for the first time, an allergic reaction does not usually occur, but rather the body forms a sensitized state. Allergic reactions will occur only when the body is exposed to the same allergen later. 2, the body has a certain tolerance to allergic reactions. When the degree of stimulation of the allergen is lower than the body’s tolerance, the body is in an allergic state, but does not develop; only when the stimulation of the allergen or other triggering factors exceed the body’s tolerance, the body will show symptoms of allergy. What are the allergic diseases? Common allergic diseases include asthma, allergic rhinitis, allergic conjunctivitis, allergic dermatitis, eczema, urticaria and so on. The main manifestations are itchy skin, wind clusters, runny nose and teary eyes, etc. In severe cases, abdominal pain, diarrhea, difficulty in whistling, and even death by shock may occur. Due to the lack of awareness of allergic diseases, many people often mistake the symptoms for a cold or enteritis when they are not obvious and do not pay enough attention to them, missing the best time for treatment, making the disease chronic and difficult to treat. Many skin diseases are also related to allergic reactions. Common allergic skin diseases are atopic dermatitis, eczema, contact dermatitis, urticaria, drug rash, etc.. The main manifestations include itchy skin, red spots and bumps. Acute dermatitis eczema patients may also blister and ooze; chronic patients will have rough and thickened skin. Patients with urticaria will have large red patches and bumps all over the body, which can subside quickly with medication, but can recur.