What cause irritation and swelling after bee a sting?

Irritation and swelling after a bee sting are primarily caused by the body's immune response to venom injected by the bee. The venom contains proteins that affect skin cells and the immune system, leading to the release of histamines and other chemicals. This reaction results in inflammation, redness, and swelling in the affected area as blood vessels dilate and fluid accumulates. Additionally, individual sensitivity to the venom can exacerbate these symptoms.