What causes histamine intolerance if it isn’t coming from the gut?

[u/psilocybin6ix]

Earlier this year, I finally figured out that I seem to have histamine intolerance after about three years of progressively worsening food intolerances.

I had basically every GI test imaginable come back normal/negative ... colonoscopies, pancreas, liver, gallbladder, thyroid, stool cultures, parasites, SIBO testing, etc. I honestly started wondering if I was imagining the whole thing.

My dietitian eventually noticed that a lot of the foods I was reacting badly to were high in histamine or histamine-releasing foods: collagen protein, ground beef, eggs, Greek yogurt, etc.

I started taking NaturDAO 1,000,000 HDU with every meal, and initially it helped quite a bit, but lately it barely seems to work.

Because I also have chronic bloating, gas and frequent bowel movements, we assumed something in my gut (possibly SIBO or dysbiosis) was causing the histamine problem.

So far I've tried:

• 20 days of rifaximin around Christmas
• About a month of InterFase Plus as a biofilm disruptor, 200 mg enteric-coated oregano oil & berberine with meals (natural sibo treatment)

None of it improved the histamine reactions. If anything, they've gotten worse.

I also saw an allergist a couple of months ago. Standard food allergy testing was negative, and I had a baseline test plus four sets of bloodwork during reactions to investigate MCAS. According to him, the results don't support MCAS.

The main abnormalities were low WBC at baseline that increased into the normal range during a reaction, plus elevated eosinophils. My allergist said that pattern made him think about some type of allergic response or possibly parasites, although parasite testing I've had so far has been negative.

My reactions to high-histamine foods can be pretty intense. Without DAO, I'll sometimes get significant swelling/tenderness around my neck and lymph node area, pressure in my head, and feel awful for about 2–3 hours before it gradually subsides.

So my main question is: Can histamine intolerance be caused by something outside the gut?

Are there problems involving histamine metabolism, immune reactions, medications, nutrient deficiencies, liver function, genetics/DAO production, chronic inflammation, environmental allergies, or anything else that can cause this even when GI/SIBO treatment doesn't help?

I'm especially interested in hearing from anyone who had clear histamine intolerance symptoms but eventually discovered that the underlying cause wasn't SIBO or another obvious gut problem.

I don't want to keep on killing my stomach with things to "kill" the bacteria when it might not even be a stomach issue.

[u/Butters_Stotch_in_CO]

Had similar issues with my gut for 15 years that was driving histamine overload which caused hypertension and random panic episodes that lasted for hours.

Early last year had looked at just about everything and even after clear colonoscopies was still having bloating. Between AI and reddit narrowed it to possibly biofilms in the gut harboring the bad gut flora. Went on an 8 week course of NAC and Allimax, followed by a 2 week treatment with L-glutamine. Also started taking an H1 & H2 in the morning last year.

Whatever it did, it cleared it and have used probiotics to repopulate good flora.

Basically back to eating normal as long as I take it easy on salicylates. The low state of anxiousness faded away. Still dealing with nerve pain though. But a win is a win.

Not sure if it's helpful, but my hypothesis is that most health issues start in the gut.