You know, I have noticed recently that when I take Zyrtec for allergies I'm having this season, I feel a bit better overall. I decided to do a quick websearch on antihistamines and found that I"m not imagining it...

It's interesting to read what mast cells do and what histamine is and how antihistamines work, and that some meds are antihistamines and we didn't realize it.

Here's one intro to a paper on a new antihistamine discovered to help in pain specifically:

"...Pain arising from distension, ischemia, and inflammation of the viscera, such as stomach, kidney, gallbladder, urinary bladder, and intestines, constitute a large part of clinically treated pains. [1] Vagal afferent system and spinal ascending pathways including spinothalamic tract and dorsal column system convey visceral nociceptive information to the higher centers of the central nervous system. [2],[3] Many of brain nuclei and regions such as nucleus gracilis, ventroposterolateral nucleus of thalamus, locus coeruleus/subcoeruleus (LC/SC), anterior and posterior cingulated cortex, and somatosensory cortex participate in the central perception of visceral pain. [4],[5],[6] Brain chemical messengers including serotonin, noradrenaline, dopamine, opiates, cytokines, and glutamate are involved in the brain modulation of visceral nociception. [4],[5],[6]

Several lines of evidence suggest that brain histamine may be involved in the central perception of pain. Intracerebroventricular (i.c.v.) injection of histamine has been shown to produce antinociception in a hot plate and paw pressure, [7] formalin, [8],[9] neuropathic, [10] and trigeminal [11] pain tests in mice and rats. Intrahippocampal microinjection of histamine produced an antinociceptive effect in the formalin-induced orofacial pain in rats. [12] It is recognized that the action of brain histamine on pain modulation is mediated through histamine H 1 , H 2 , and H 3 receptors. [7],[8],[9],[10],[11],[12]

There are no reports regarding the direct effect of brain histamine and the involvement of its central H 1 and H 2 receptors in the acetic acid-induced visceral nociception in rats. In one study, centrally administered histamine produced antinociception in the acetic acid-induced writhing test in mice. [7] Moreover, the involvement of brain histamine H 1 and H 2 receptors was reported in the phenylquinone- and acetic acid-induced visceral nociceptive tests in mice. [13],[14] Therefore, this study was designed to investigate the effect of i.c.v. injection of histamine, chlorpheniramine (a histamine H 1 -receptor antagonist), and ranitidine (a histamine H 2 -receptor antagonist) on the acute visceral nociception induced by i.p. injection of acetic acid in rats.
..."
from http://www.ijp-online.com/article.asp?issn=0253-7613;year=2010;volume=42;issue=5;spage=289;epage=292;aulast=Zanboori;type=3