Immediate allergy, also known as Type I hypersensitivity or immediate hypersensitivity, is an exaggerated immune response triggered by a specific allergen upon its contact, ingestion, inhalation, or injection into an individual's body. This type of allergic reaction usually occurs within minutes or up to a few hours after exposure to the allergen.
In immediate allergy, the immune system reacts vigorously to the presence of the allergen by producing a type of antibody called immunoglobulin E (IgE). These IgE antibodies attach themselves to specialized cells called mast cells and basophils, which are found in various tissues throughout the body, particularly in the respiratory and digestive systems, as well as the skin.
Upon subsequent exposure to the same allergen, the allergen binds to the IgE antibodies already attached to the mast cells and basophils, stimulating the release of multiple potent chemical mediators, such as histamine, leukotrienes, and cytokines. These mediators cause a cascade of symptoms, including itchiness, redness, swelling, sneezing, coughing, wheezing, hives, nausea, vomiting, and in severe cases, anaphylaxis.
Immediate allergies can be triggered by a wide range of substances, such as certain foods (e.g., peanuts, shellfish), medications (e.g., penicillin), insect venom (e.g., bee stings), animal dander, pollen, dust mites, and mold spores. It is important for individuals with known immediate allergies to avoid exposure to these allergens whenever possible and to carry appropriate medication, such as antihistamines or epinephrine, in case of accidental exposure.
