The warnings on labels of certain antihistamines, that drowsiness may occur, are there for a reason: histamine promotes wakefulness (1); therefore, blocking it can induce drowsiness. In fact, most medications marketed as sleep aids contain an antihistamine for this reason.
What does that mean for the rest of us? If you have a buildup of histamine, it could be keeping you up at night.
Within the brain, histamine is responsible for regulating the cycle of sleeping and waking. Histamine is most active while we’re awake, and is more active during the phase of the sleep cycle that most closely resembles wakefulness than it is during deeper sleep. Histamine doesn’t just promote wakefulness in general, it also has an impact on the biological “clock” that regulates our circadian rhythm (the internal 24 hour cycle that tells us when to sleep, wake up, eat, etc.).
Improper or insufficient synthesis of histamine can lead to somnolence (excessive sleepiness), while excess histamine can lead to insomnia, a common problem among people who suffer from histamine intolerance.
Avoiding high-histamine foods– especially later in the day– might lead to a better night’s sleep for those with a histamine intolerance. Furthermore, as the act of digestion itself triggers the release of histamine, avoiding eating late in the evening can help.