Severe life threatening allergic reactions are also referred to as Anaphylaxis. Any substance entering the body may become what is called an ‘allergen’ causing an allergic reaction in some people. Anaphylaxis may occur due to drug allergies, food allergies or insect bites/stings. Such allergens may even trigger asthma in some cases though very rare.
Allergens like venom from insect bites or certain drugs could prove toxic. On the other hand, certain allergens especially food substances may actually not be a toxic substance but the body’s immune system mistakenly recognizes it as a toxic foreign particle and overreacts to this allergen by releasing chemicals. These chemicals cause the symptoms of allergic reaction like itching, abdominal pain, nausea, dizziness, cough, wheezing or breathing problems.
Foods especially dairy products, eggs, peanuts, food colorings may trigger allergy in some people. After exposure to the same allergen again, anaphylaxis happens quickly. Tissues in various parts of the body produce a substance called histamine. Histamine is an active substance found in many plants, bacteria and insect venom. It is released as a part of immediate reaction of the bodily tissues to injury caused by physical damage, infection or allergic reaction. Histamine causes difficulty in breathing by blocking the air passage.
The immune system’s overreaction to a harmless allergen causes release of histamine in large amounts. Immune system proteins called antibodies bind to the allergen to remove them. In this process too, histamines are released by the cells. Histamines cause allergic reactions like swelling, watery eyes, running nose, sneezing etc. Sometimes exposure to already encountered allergen may also prove fatal due to constriction of air passage.