A Type I allergic reaction, also known as immediate hypersensitivity or anaphylactic reaction, is a specific immune response that occurs rapidly after exposure to an allergen. It is the most common form of allergic reaction. In this type of reaction, the immune system of an individual, who is sensitized to a particular allergen, reacts excessively when exposed to that allergen again.
When an allergen enters the body, it stimulates the production of specific IgE antibodies by B cells. These IgE antibodies attach themselves to mast cells and basophils, which are cells of the immune system that play a role in inflammation. Upon reexposure to the allergen, it binds with the IgE antibodies, leading to the release of histamine and other chemical mediators. Histamine causes blood vessels to dilate and increases the permeability of blood vessels, resulting in symptoms such as itching, hives, nasal congestion, and swelling.
Common triggers for Type I allergic reactions include pollen, animal dander, certain foods, insect stings, and medications. Symptoms can range from mild to severe, and in some cases, can be life-threatening, resulting in anaphylaxis. Anaphylaxis is a severe systemic reaction that affects multiple organs of the body and requires immediate medical attention, often with the use of epinephrine.
Treatment for Type I allergic reactions typically involves avoiding exposure to known allergens, taking antihistamines to relieve symptoms, and in severe cases, using epinephrine to manage anaphylaxis. Allergy testing can help identify specific allergens, facilitating proper management and prevention of future reactions.
