Are quercetin and/or stinging nettle actual antihistamines?

March 4, 2011 8:12 AM

Are quercetin and/or stinging nettle actual antihistamines?

I know from experience that a few herbal remedies like quercetin and stinging nettles help me with my hideous allergies (the nettle lozenges from NewChapter are pretty amazing, but they only last 3 or so hours at the most and are super pricey). Several things I've read about them indicate their ability to 'balance histamine levels' and other potential pseudo-sciencey claims, despite the fact that I'm pretty sure they've both been proven actually effective to some degree. I know quercetin is a mast-cell inhibiting bioflavonoid, so based on that description I'm pretty sure it's not an antihistamine, but I'm uncertain as to the action of nettles being truly "antihistamine" or not from my googling even though folks say it is here and there.

I'm going to have some bloodwork done, and they suggest not taking antihistamines 3 days prior to the testing, so I'm going to lay off anything that might possibly be from the antihistamine family just to be sure, including either of those.

But my question is, are either quercetin or stinging nettle considered true "antihistamines"?

posted by bitterkitten to Health & Fitness (2 answers total)

Best answer: A cursory stroll through the literature suggests that quercetin has the ability to inhibit histamine release in vitro caused by some (but not all) inflammatory stimuli. That's different from a traditional antihistamine, which antagonizes histamine receptors and thus acts in a more general way. I saw no immediate evidence demonstrating the effect in vivo, meaning it's anyone's guess as to whether it can actually reduce allergic reactions in humans. I'd suggest skepticism.

For stinging nettle, you need to make a distinction between the stinging hairs versus, for instance, extracts made from the leaves. The stinging hairs have a highly inflammatory effect; they are most definitely not antihistaminergic. In fact, they contain histamine, among other irritants. Leaf extracts may be a different matter, as I was able to find a few studies suggesting they lower pro-inflammatory cytokine levels in the blood. Again, this is not a traditional antihistamine mechanism, and it may or may not have any practical effect on allergic response. Inflammation is a great deal more complicated than ON/OFF, and these are pretty isolated studies. Take this sort of evidence with a grain of salt.
posted by dephlogisticated at 9:13 AM on March 4, 2011

Response by poster: Thanks deph! Ya, I believe the nettle preparations sold are typically from the leaves of the stinging nettle plant. The hairs are another matter, for sure.
posted by bitterkitten at 9:32 AM on March 4, 2011