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Whenever there’s a topic that keeps coming up, I like to write about it. The big question right now is…what about quercetin?

What really propelled me to write this post is that one of my alopecia clients who also has Hashimoto’s has had a lot of anxiety about occasional use of quercetin for her allergies—she was afraid that it was going to slow her thyroid function and cause her to lose the ground she’s gained in her coaching program.

The short story is that:

- Quercetin shows some benefit for those with Hashimoto’s
- Too much quercetin can slow thyroid function
- Quercetin also has some hair growth benefits
- The combination of nettles and quercetin has been shown to work as well as or better than many over the counter antihistamines, especially Zyrtec—this has big implications for the alopecia community, so keep reading
- Helps to detox the spike proteins from the Covid shot.

So yes, when it comes to thyroid health, we don’t want one foot on the gas and one on the brakes. This reminds me of the pervasive question about iodine supplementation, which is another “goldilocks” nutrient—you don’t want too much or too little. I think this is true with most things!

To clarify—iodine is essential. Quercetin, not so much, although there are a variety of benefits. There are many foods that contain it and it’s not that common to find someone randomly supplementing with an isolated quercetin outside of the presence of high blood pressure or histamine/mast cell issue, which is very common in the alopecia community.

What is quercetin?

Quercetin is a powerhouse polyphenol antioxidant and bioflavonoid. It has anti-inflammatory properties and is also an immune system modulator and stabilizer—it helps to quell “immune excess” and assists our cells in maintaining homeostasis under stress. This is one of the ways that it’s beneficial for those with Hashimoto’s—or any autoimmunity.

It helps our system—including thyroid cells—combat free radicals, those unstable molecules that can result from exposure to tobacco smoke, radiation, pollution, and other environmental chemicals and substances.

It’s found in many fruits and vegetables:

- Primarily: onions (especially red), grapes, berries (especially cranberries), cherries, broccoli, citrus fruits, apples, sage, tea, parsley, and red wine
- Other fruits include: plums, apricots, capers, and black currants
- Other vegetables include: kale and spinach
- Herbs: watercress, dill, tarragon, and coriander
- Raw cocoa powder

It’s said that boiling can destroy almost 30 percent of the quercetin in food.

Quercetin and your thyroid 

Quercetin is said to reduce activity of an enzyme needed to convert that iodine into thyroid hormone and make it available for use.

But the use of quercetin hasn’t been linked to hypothyroidism per se.

As this abstract states, “Concerns have been raised about the potential toxic effects of excessive intake of quercetin and several studies have demonstrated that flavonoids, included quercetin, can interfere with thyroid function.”

Note the word, excessive. If you’re supplementing with quercetin moderately or intermittently, as many do to manage allergy symptoms (see more below), it’s not likely to slow the thyroid in any substantive way.

That said, “excessive” can mean different things to different people. Often, too much quercetin intake can result in tingling, headaches, and nausea, so it’s possible that you could consider these symptoms your “shut off valve.” You may want to speak with your provider about appropriate dosing.

My non-medical opinion is that taking moderate amounts of quercetin to manage occasional or moderate allergies isn’t going to slow your thyroid in any substantive way.

Quercetin and hair growth

A primary trigger for hair loss/alopecia is mast cell degranulation. It’s often referred to mast cell activation syndrome (MCAS) or mast cell activation disorder (MCAD).

This is a topic that’s deserving of another post, but know that degranulated mast cells can cause people to not only become histamine intolerant, but also histamine overproducers—I realize that there’s a nuanced difference between the two.

Histamines are those compounds that incite an allergy response like hives, runny nose, sneezing, post nasal drip, itchy skin, and itchy eyes—the H1 response.

The symptoms of MCAD run the gamut, but what’s not well known is that it’s one of the primary drivers of alopecia by way of H2 receptors, which are primarily found in the gut.

Stabilizing my mast cells brought my alopecia ophiasis (no hair above my ears, wrapping around the back of my head) to a screeching halt and catapulted me back to a full head of hair.

One of the first questions I ask my alopecia clients is—do you have allergies? Most say yes. And they don’t necessarily have to be seasonal allergies.

Yes, I’d had seasonal spring allergies and a few years ago, I discovered that the combination of quercetin and nettles put a complete smackdown on my symptoms. Again, it’s been said to work better than Zyrtec.

I wasn’t interested in taking over the counter antihistamines, so this discovery was life-changing. My clients have been shocked at how well quercetin/nettles works and they’ve been thrilled to get off of the over the counter meds. Yes, it works that well.

What I later found out is that indeed, quercetin offers some hair growth benefits. According to Dr. Josh Axe, “A 2012 study conducted on mice found that quercetin was effective in stimulating hair regrowth when compared to placebo injections.”

According to this abstract, “Systemic delivery of quercetin by intraperitoneal injections prevented/reduced spontaneous onset of AA (alopecia areata). Our results demonstrated that quercetin provided effective treatment for AA as well as prevention of onset of AA in the C3H/HeJ model, and warrant further clinical studies to determine whether quercetin may provide both treatment for preexisting AA and prevention of recurrent AA. The ready availability of quercetin as a dietary supplement may lead to increased patient compliance and positive outcomes for AA.”

So my belief is that for those with alopecia who have allergy and mast cell issues, quercetin may provide a dual benefit—reduction of histamines as well as unique hair growth properties.

Actually, a triple benefit for some, as many with an inability to break down histamines are deficient in the enzyme DAO (diamine oxidase). Quercetin just happens to be an alternative to DAO supplementation. I’m not crazy about DAO as a supplement because it’s said to be an unstable, pork-derived compound.

Low and Slow

But…I’m not in favor of taking loads of quercetin or taking it long term. You want to discover why you’re histamine intolerant and have histamine overload, which is often a case of MCAD. You’ll also want to find what it is in your environment that you’re reacting to.

The best supplement for stabilizing mast cells and putting a smackdown on histamines? Black seed oil/nigella sativa. A mere teaspoon a day of a high quality black seed oil is enough—maximum two teaspoons.

And get this…black seed oil also has hair growth properties. And anti-cancer, anti-inflammatory, thyroid-boosting, immune modulating properties. My favorite brand is Heritage, which you can get on Fullscript. Remember, you only need 1-2 teaspoons. If you’re in the U.S., see below for ordering information from Fullscript.

And get this too—quercetin can be applied to the scalp. There used to be a company that made quercetin cream and now I can’t find it. But you can get liquid quercetin from Source Naturals.

Again, my favorite brand of black seed oil is Heritage and my favorite brand of the nettles/quercetin combination (yes, you can get it in one product) is Designs for Health. You can order both below through Fullscript. 

As many of you have heard me say over the years, I like to take a “food first” approach with most things. See the list above of quercetin-rich foods, but yes, supplementing can be beneficial if you have allergies and especially if, like me, you don’t want the over the counter antihistamines. Just keep in mind that you don’t want to go nuts with quercetin—you don’t want to over-rely on it.

And if you have Hashimoto’s—or any autoimmunity—remember that quercetin has anti-inflammatory, immune modulating benefits. I’d never rely solely on it to take care of these imbalances (I’d focus largely on turmeric, essential fatty acids, glutathione, and minerals), but you could consider quercetin icing on your anti-inflammatory, immune modulatory cake if allergies are also in the mix.

The goal, as with all supplements—is to use them for their therapeutic benefits, to take advantage of the beneficial therapeutic index, and get off of them.

How to order

If you’re in the U.S. and interested in the Heritage black seed oil, the Designs for Health quercetin/nettles, or anything else for you or your family…

Set up your U.S. Fullscript account here >

And feel free to peruse my Categories to see some of my best thinking on other supplementation.

(If you’re in Canada or Europe, reach out and I’ll hook you up with a colleague’s dispensary. I can’t guarantee availability of the same brands.)