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Pine nuts look so innocent, but thousands of people have been left with an overwhelming and lasting bitter taste in their mouths after eating them. "Pine mouth syndrome" isn't dangerous, but it sure is unpleasant. Here's what you need to know.

The overwhelming metallic taste in my mouth was merely unpleasant at first — I vaguely suspected that my new toothpaste might be to blame and assumed it would pass soon enough. As the sensation didn't subside but actually grew worse, however, I did what twenty-first century folks with weird medical issues do — I turned to Google. Pages and pages of search engine results later (I tried both "bad taste in mouth" and "metallic taste in mouth"), I was starting to get a little worried. Anything from a stroke to Bell's Palsy and from liver to kidney problems could, my friendly neighborhood search engine told me, explain my lone but disturbing symptom. Medications can also be to blame, but I wasn't on any associated with this symptom. 

To make a fairly long and boring story short, Google and I eventually retraced my steps to my last trip to the grocery store, where I'd picked some (imported Chinese) pine nuts up on special offer. What was meant to be a treat turned quite sour, or rather metallic. I turned out to be suffering from what's colloquially been termed "pine mouth". It takes longer than you want to clear up, but doesn't seem to be dangerous in any way — and I'm writing about it both to raise awareness and to help clarify that you're not actually dying if you get it, too. 

'Pine Mouth'? Is That Even A Real Thing?

You bet, and entire research studies have been conducted into the topic. One study entitled “Pine Mouth” Syndrome: Cacogeusia Following Ingestion of Pine Nuts (Genus: Pinus). An Emerging Problem? even references our very own SteadyHealth, where pages upon pages of community member comments debated the cause of a bitter or metallic taste in the mouth, some of which were traced back to pine nuts. [1, 2]

The first documented instance of cacogeusia — a bad taste not caused by something you're currently ingesting or have just finished ingesting, also called metallogeusia if the taste is metallic or bitter — linked to pine nuts took place in Belgium in the year 2000 and was written about in 2001 [3].

Thousands more cases of "pine mouth" or "pine mouth syndrome" have appeared in the medical literature since that time, particularly in France, the UK, and the US [4], and some of the victims of this unusual problem were so worried they reported it to poison control. Acknowledging that not everyone who experiences this problem seeks medical help, the authors of the above study also wanted to find out what people said about the condition online.

They found that cases of pine mouth seem to be on the increase, and further noted that:

  • The bitter or metallic taste sets in anywhere from one to three days after ingesting as few as 10 pine nuts. 
  • Besides a metallic or bitter taste, some people also experience nausea and abdominal cramps. (Another study additionally found that some people have headaches and diarrhea [4].)
  • Both raw and cooked pine nuts can be implicated, and though some other studies specifically point to Chinese pine nuts as a cause, other species can cause pine mouth as well. 
  • The condition resolves itself within a matter of weeks with no further consequences. 

So, What Actually Causes Pine Mouth Syndrome?

Nobody is quite sure yet, but some pointers have been identified:

  • The metallic taste people with pine mouth syndrome experience may be caused by some unidentified toxin [5]. 
  • Some people may be genetically predisposed to experiencing this awful taste after eating pine nuts [6].
  • The pinolenic found in pine nuts may induce a complex hormonal process that leads to excess bile production, in turn giving you the now infamous metallic taste [7]. 

Though various species of pine nut can induce pine mouth syndrome, two have especially been implicated — Pinus armandii (Chinese white pine) and Pinus massoniana (Chinese red pine). Other species can cause pine mouth syndrome as well, mind you, and not everyone, or even the majority of people, experiences a metallic taste in the mouth after consuming them. 

Can I Prevent Pine Mouth Syndrome?

The primary offending species and the one that gave me pine mouth, Pinus armandii, is no longer imported to the European Union [7], where I live. Still, I can tell you that I've gone to fairly extreme lengths to avoid pine nuts since the whole saga, even making my own pesto sauce with hazelnuts instead of pine nuts. I figure that foregoing tasty pine nuts is more than worth it if it means I won't have to have a bad taste in my mouth for weeks on end again! Considering the possibility that your susceptibility to pine mouth is indeed genetic, I'd advise you to avoid pine nuts too if you or someone in your immediate family has experienced pine-related metallogeusia before. 

If not? You probably don't have anything to worry about. I do hope that you keep this information in the back of your mind, however, so that you don't immediately worry you may have a life-threatening or life-altering health condition if you do happen to experience a pervasive metal or bitter taste in your mouth one day. Should you have eaten pine nuts, you can probably rest assured that you'll be just fine as long as you don't keep eating the offending food. It will just take a while — a bad while, to be sure, but it'll pass. 

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