A hormone/chemical transmitter (biogenic , similar to
) involved in local immune responses,
regulating stomach acid production and in
allergic reactions as a of
When released from , histamine causes
and an increase in permeability of blood vessel walls.
These effects, in turn cause the
familiar symptoms of allergy including a runny nose and watering eyes.
When released in the lungs, histamine causes the to swell shut in an
attempt to close the door on
and keep them out.
Unfortunately, the ultimate result of this response is the wheezing and difficulty in breathing seen
in people with
- an occasionally deadly allergic complication which kills an estimated 4000 Americans yearly.
See also : .