Histamines are biochemicals produced by normal human immune cells and gut bacteria.And they are fascinating. The first surprise? Histamines mainly function as neurotransmitters. It’s a brain chemical, like serotonin or dopamine. Antihistamines are sometimes used to treat anxiety! So, how come when we say histamines, most people think antihistamines, as in something to get rid of allergy symptoms? Histamines get connected to allergic response because it is stored and released by mast cells. Mast cells are specialized white blood cells, which are part of our immune system. There are four types of histamines that we know of:
- H1 histamine is known for its role in hives, allergies, and the sleep/wake cycle. (If an H1-blocking antihistamine ever made you drowsy, that’s why!)
- H2 releases hydrochloric acid in the stomach (Pepsid is an H2-blocking antihistamine).
- H3 is more like a classic neurotransmitter, likely involved in OCD, sleep disorders, and ADHD.
- H4 is involved in hives and asthma.