Histamine Intolerance & DAO: Answers to Your Questions

So many of you emailed me with questions that I put together a Q&A. This is a far broader topic than I can summarize (even with six hours of writing!), but it’s a start. The formatting is ugly and you’ll have to scroll through a lot of text. I’m prioritizing your access to the information over making it look nice. Expect typos.

I don’t have allergies. Could I still have an issue with histamine?

Absolutely. I don’t have allergies either and have no allergy symptoms. Right now, I can only present myself as a case study and say that I’ve encountered multiple people in forums who are histamine-intolerant and do not have allergy symptoms. This is on my list of topics to investigate and I’ll present real data when I can.

What’s the name of the supplement you use and where can I buy it?

The actual name is Histamine Block and it’s available on Amazon. Histame is probably the most popular DAO supplement. It costs less than Histamine Block, but is also less potent. (I’m an Amazon affiliate, so I’ll get a small portion of the sales if you purchase through one of those links. I have no relationship, financial or otherwise, with any company that manufactures or sells DAO.)

What is an HDU?

HDU stands for “histamine digesting unit” and you’ll see it listed on every DAO supplement. It appears to be a scientific term that’s been co-opted for marketing, but the two don’t align. Currently, I only use the numbers to compare the strength of one supplement to another. I’ve also found that, so far, 20,000 HDU is most effective for me.

I don’t get a migraine or headache every time I eat, but I do sometimes and can’t connect it to any particular food. Could DAO help me?

Quite possibly. I think I’m fairly rare to have eating anything trigger migraines (or histamine intolerance symptoms). Far more common is for people to have trouble with particular foods. Certain foods naturally contain histamine or are “histamine liberators,” both of which result in even higher amounts of histamine to your system than is part of the normal digestion process. Most people don’t have as much trouble with the normal histamine release as I do, but run into problems when they eat foods that contain or liberate additional histamine.

What foods contain or liberate histamine?

This is a landmine. The short answer is that you will find many conflicting lists of histamine-containing foods online. Searching forums will confuse you even more. Here’s the list of histamine-containing foods that’s most widely regarded as accurate. You’ll notice that it also includes foods containing tyramine. The two are related (both being amines) and there’s a lot of overlap between them. Tyramine has long been suspected to trigger migraines, and possibly other headaches, so a list restricting both is a good place to start.

Starting an elimination diet is overwhelming and time-consuming and I have tons of guidance to offer. On another day.

Will DAO work if I don’t change my diet?

Maybe, but the odds are against you. Here’s a full post on DAO and diet. lAdded Dec. 3, 2014]

Are DAO supplements safe?

Yes, according to the dietician I’ve been consulting with (who is as close to an expert on this topic as you can get), my naturopath, and the recent DAO for migraine prevention study. Any of the DAO that isn’t used is flushed out through the digestive process. It’s not absorbed in any way, nor does it stick around for more than a few hours. (The information in the last two sentences is from my naturopath. I’m going to double-check it with the dietician.)

Do DAO supplements have any side effects?

None of the 117 patients who completed the aforementioned study of DAO for migraine prevention reported any side effects. That’s pretty much unheard of for a study of a drug or supplement. Online forums are a little different (and also not part of a controlled experiment).

The main side effect I’ve seen on forums is that some people say it makes them shaky. That was true for me initially. Taking the DAO only five minutes before I ate seemed to help, I think because it didn’t sit in my stomach for too long without food. I did that a few times before moving to taking it 10 minutes before eating. My intuition is that it is more effective if it has more time to release before encountering food, but I don’t know that for sure. I’ll ask my dietician about it.

Someone just told me that she flushes and sweats when she uses any brand of DAO supplement. That’s the first time I’ve heard of that side effect and I don’t know how common it is.

I sometimes react to natural supplements. Am I likely to react to this one?

I’ve demonstrated so much intolerance for natural supplements that my naturopath only prescribes pharmaceuticals for me(!), but I’m doing fine with this one. Use your own judgment to decide if the risk is worth it for you. If your reactions tend to be severe or you think the risk is too great, consulting with a naturopath or dietician before taking it would be wise.

Where did you learn about DAO supplements?

The dietician and my naturopath both recommend it. It is also commonly used among people with histamine intolerance, so it’s mentioned on forums a lot.

If I have a histamine issue, could I take antihistamines instead?

If your triggers are connected to food or eating, it appears to be more effective to take DAO than an antihistamine. Adding the enzyme you’re deficient in seems to address the problem more directly than an antihistamine. Antihistamines can also cause a strong enough rebound effect that the dietician warns against them. For now, I’m still taking 12 mg of cyproheptadine, a prescription antihistamine used for migraine prevention, each day.

If you do decide to try an antihistamine, patients with histamine intolerance (whether their symptoms are migraine, headache or something else) seem to have more success with older drugs, like cyproheptadine and Benadryl, rather than the newer ones (Allegra, Claritin and Zyrtec). I don’t know why.

What’s “histamine intolerance”?

Histamine intolerance (often referred to as HIT) is when someone has a reaction to ingesting histamine and/or the release of histamine that accompanies digestion. The reactions vary, but can include diarrhea, headache (and migraine) nasal congestion, wheezing, low blood pressure, irregular heart beats, rashes, flushing, and itching.

Histamine intolerance isn’t a food allergy, but is a food sensitivity (it’s an important distinction). It’s not widely known about, but is starting to get a lot of attention in parts of Europe (especially the U.K.) and Australia. Thanks to the internet, the information is accessible if you know where to look.

For what it’s worth, I haven’t been diagnosed with histamine intolerance, nor have I diagnosed myself with it. But it’s the best search term to find information on histamine and food, and it’s the term most people who have issues with histamine apply to themselves.

Why do you qualify so many statements with “appears to” and “seems to”?

There are a lot of unknowns about histamine and DAO. Finding solid information online is difficult and patient groups lean toward pseudoscience. While I believe I’ve sussed out reliable information, I would rather say I’m not absolutely sure about something than discover that I presented incorrect answers as fact. If I continue to feel as good as I have this past week, I’ll soon be combing through journal articles at the local university library and will pass on what I uncover.

What else do I need to know?

I’m sure I’ll be sharing much more as the week — and year — goes on. If you want to know more NOW (I sure did when I first started learning about this), here are some places to get started:

  • Histamine Intolerance Awareness (website) — The food list on this site is kind of difficult to follow and some of the inclusions are questionable, but the rest of the information is a very helpful start. Genny Masterman, who put this site together, has a book called What HIT Me? It’s a good introduction and is written in an accessible, easy-to-follow style, but I found the meatiest information to be covered sufficiently on the website.
  • Dealing with Food Allergies (book) — This is my favorite book for the general public, even though the title is misleading (histamine intolerance is NOT an allergy). It doesn’t contain a lot of detail, but hits all the important points and has clear, well-organized food lists. Be sure to check the sections on both histamine and benzoates (benzoates are histamine liberators). I think there’s a section on tyramine as well. The author, Dr. Janice Joneja, the dietician I’ve been working with.
  • Histamine and Histamine Intolerance (journal article) — If you’re willing to wade through an academic article, this is the one to read. I’m working on summarizing it, but not sure when it will be ready to post.
  • Other websites — If you come across another website and are wondering how accurate it is, please ask me. I’d like to have multiple sites to refer people to and it would be helpful to see which sites people who are new to this topic find.

Please remember that I’m not a medical professional and nothing on this site should be considered medical advice. I’m a patient reporting on what I’ve learned and experienced. I hope that it can help you with your own sleuthing, but please solicit the input of your health care team.

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