What are the consequences of the allergic cascade?
Now that we understand how the allergic reaction develops, let’s review the various changes that occur in the body as a result of these early and late phase reactions. When histamine is injected into the skin, a technique used in diagnosing allergies, a reaction that can mimic an allergic reaction occurs. The histamine injection prompts the development of a pale, central swollen area that is caused by fluid leaking out of local blood vessels into the adjacent tissues. This localized reaction is called a “wheal.” A red “flare,” which sometimes has a warm feeling due to inflammation, surrounds this “wheal.” Itching occurs because histamine irritates the nerve endings in the skin. This early or immediate response peaks at about 15 minutes and fades within 90 minutes. Sometimes, the immediate effects are followed by a late phase reaction that occurs about 4 to 6 hours later and can last up to a day. Allergens, such as ragweed pollen, react with the tissues lining the inner surfaces (membra
