Antihistamines could even work without any allergy since they are typically used as mild sleeping aids. They are also used often off-label for stress reduction. [0]
[0] https://fherehab.com/learning/surprising-antihistamine-anxie...
[0] https://fherehab.com/learning/surprising-antihistamine-anxie...
With regular use antihistamines quite quickly lose their drowsiness effects. But it's definitely a nice side effect for sleeping challenged folks. Azelastine is a second generation antihistamine so not particularly drowsiness inducing.
One of the interesting Azelastine quirks, is it's apparently somewhat antiviral [1].
https://www.health.harvard.edu/mind-and-mood/should-i-worry-...
> Theoretically, these drugs might increase the risk of dementia by blocking a particular brain neurotransmitter or increasing brain inflammation. In the past decade, several studies have suggested that these pills might increase the risk of dementia, while other studies have found no risk. And all the studies are inherently flawed.
Older first generation antihistamines such as Diphenhydramine (Benadryl), Doxylamine (Nyquil) have substantial Anticholinergic activity.
A lot of the second generation antihistamines have no significant Anticholinergic activity, eg. Azelastine.
Benadryl and Nyquil are terrible drugs. Why they haven't been phased out is beyond me. At least Azelastine is now OTC in the USA.
But it is one of the more anticholinergic second gen antihistamines, make of that what you will, still miles behind something like Benadryl. Fexofenadine is apparently a less anticholinergic alternative.