How does 2C-B work in your body?

Serotonin is a neurotransmitter that is active in the nervous system, both inside and outside the brain. It is responsible for the regulation of mood, sleep, sexual behavior, temperature and appetite, among other things.

2C-B binds to serotonin receptors in the brain, which may explain its hallucinogenic effects. It kind of pretends to be serotonin, but doesn’t exhaust it. Unlike some amphetamines (eg XTC), 2C-B does not seem to deplete the brain’s stores of serotonin.
This suggests that it is unlikely to have the neurotoxic properties of amphetamines in common doses, and the associated brain damage. It also means that some risks are less relevant, such as water intoxication and overheating.

By stimulating the serotonin receptors, the functioning of the brain changes. For example, it changes the functioning of the visual cortex, the part of the brain that deals with seeing. Because that part of the brain works differently, what you see (with eyes open or closed) changes.