Allergies

Allergies/Hypersensitivity Immune System overreacts to the presence of a harmless antigen causing tissue damge Tend to get worse with each exposure

Immediate/Acute Hypersensitivity Most common Triggered by the release of histamine Histamine causes capillaries to become dilated and leaky, and the release of mucus Common symptoms – runny nose, watery eyes, itching, hives

Anaphylactic shock Body-wide acute allergic response Fairly rare Occurs when allergen directly enters blood and circulates throughout body Swelling can block airways Epinephrine reverses symptoms (constricts blood vessels) Ex. Bee sting, spider bite injections

Delayed Hypersensitivities Occur about 1 – 3 days after exposure Involve the release of lymphokines instead of histmines Usually presents as dermatitis Ex. Poison ivy