What Does Histamine Do?

Histamines in the human body cause the contractions of muscle tissue in the lungs, uterus and stomach, according to Encyclopaedia Britannica. Histamines also dilate blood vessels, accelerate the heart rate and increase stomach acid production. This protein serves as a neurotransmitter between the nervous system and other cells in the body. Systemically, the most obvious sign of a histamine reaction is inflammation.