When partially digested nourishment is involuntarily ejected through the mouth, one of the first reactions is to wonder what caused it to happen. Was rancid meat recently consumed? Is there a norovirus going around?

Sometimes excessive alcohol is to blame and there isn’t a lot of detective work necessary. When that isn’t the case, however, the cause of a sudden retching can be difficult to track.

I have some recent experience as a vomit detective, following an incident that preceded the Christmas holiday. After a full month on the case, I can confidently state that the evidence points toward the culprit being either a cookie, a bowl of chili, or really just about anything else I encountered around that time.

That’s right, I’m getting ready to wrap up my investigation and file it as a cold case.

What’s worse is that information gathered in my latest probe has called into question a case from 2015. I might have wrongfully convicted a local fast-food chain restaurant of food poisoning.

That story was shared in an essay titled “A Lifetime of Vomit.” To summarize it here: I had not vomited for more than 26 years, then suddenly had a prolific eruption about 14 hours after eating at an unnamed Duluth establishment. When I wrote that essay I was pretty sure the fast-food lunch was to blame, but I nonetheless refrained from naming the eatery in the essay. The evidence seemed strong but circumstantial. My judgement was to convict and not sentence, I guess.

By the way, essay readers might be wondering why I feel it’s necessary to publicly report every time I puke. Let me emphasize that I have vomited just twice in the past three decades. That’s notable.

Vomit is, of course, a controversial topic because it is disgusting and hilarious at once. I read “A Lifetime of Vomit” a couple years ago to an audience of about 50 people. Most of them laughed with no inhibition, but a few people stood up and walked out. I absolutely understand that. Anyone feeling queasy right now should indeed read the Constitution instead. Don’t provoke a sensitive tummy.

Now, on to the latest case:

It was Dec. 18, and my wife Stephanie had just prepared a chili dinner. As part of my usual role of being a sardonic jackass, I looked at the chili and commented that it looked like the same chili I barfed all over our walls five years ago. This was annoying to my bride, because she insists we’ve eaten this same chili numerous times and not gotten sick, and that the chili we ate before I got sick in 2015 was a different chili recipe, and the 2015 chili didn’t get her sick. So all evidence in that case points to my restaurant lunch, right?

Well, what are the odds that since my previous gut trauma I ate this chili numerous times, but then suddenly this time decided to take note of it and remark about how it strikes me as a potential danger to my health about 20 hours before the intestinal violence again occurred?

Any good vomit detective knows, however, that a simple transmission of a gastrointestinal virus could have happened at any point in my daily routine of hanging around disgusting people and handling the same doorknobs and pocket change. So diagnosing each case is mostly guesswork.

Although the chili is a target in my investigation, I do feel obligated to mention I really enjoyed it at the time I was eating it. And Stephanie baked some good bread to go with it. No one ever blames bread for vomit.

We had a good night and I went to sleep feeling content. I woke up early the next morning to attend one of those local business group things in which area professionals gather to spread germs. I drank a cup of coffee and ate a Christmas cookie. The probability for contamination there cannot be discounted.

In the afternoon I ran three errands, one of which might have involved a handshake but I can’t remember for sure. I also shopped at a large retail store. Maybe I was already infected and was just spreading it around so the rest of Duluth could sprint to the nearest toilet a few hours after me. Or maybe I ironically acquired a norovirus while buying the very supplies I would later use to clean up my vomit.

Though it implicates me as a suspect in someone else’s investigation, I do have to acknowledge that I started feeling uncomfortable before my afternoon chores. So I was likely at my most contagious while I was traipsing around town touching various countertops, chair arms, pens, drinking fountains, credit card readers, etc.

When I got home I immediately turned on the television and curled up under a blanket. The chills were setting in, but since I’d made it almost five years without vomiting — after a previous streak of 26 years — I was confident that relaxing and streaming a few TV shows would keep me from streaming chili out my stretched maw.

My plan worked for about two hours, and then with little warning I hurled chili onto my chest. I had only started to stand up, then had to sit back and attempt to contain the purgings on my shirt. I was mostly successful, spilling just a bit onto my pants and the bathroom rug on my way to the proper receptacle.

After this excellent abdominal workout my body temperature rapidly rose. Just two minutes earlier I was shivering under my blanky, now I needed to strip — which was fine because my clothing required a good dunking in a utility sink anyway.

Fun fact: Someone was supposed to stop by to look at a bed I was selling on Craigslist, but she cancelled at the last minute. If she had showed up it would have been right about the time my friend Ralph paid his visit.

Throughout the rest of the day my stomach refused to settle, so I opted to sleep on the couch. This was a good idea, because I experienced two rounds of heaving bile into a bucket overnight. Which raises the mathematical question of how vomit counts are tallied. It seems there are two sets of rules. If I’m telling you about this particular incident, I should say I threw up three times. But when vomiting is measured over years, the sessions get merged into single pukes. So I would say I threw up three times when I was sick in December, but I would say I’ve vomited twice in the past 30 years. Isn’t mathematics fascinating?

Anyway, the next day I was fine, except for soreness from the ab workout and a temporary feeling that every kind of food in the world might be absolutely disgusting to me forever.

Stephanie emerged from the bedroom with this morning greeting: “Happy birthday!”

Oh, yeah. That’s right. It was my birthday.

And then the day after that, Stephanie got sick. She got it worse than me. I think there were maybe seven rounds, all during daytime hours. That meant I had to watch her toss her guts while knowing the whole time I was responsible for the contamination that led to it.

Or was it the chili?

I’d really like to blame the chili. It would be nice to know I could greatly reduce the chance of this ever happening again by simply refraining from the consumption of a tofu, smashed tomato and pepper stew. But it was probably just a horrible coincidence that two upchuck fests in a row followed chili dinners. The odds are always in favor of a coincidence.

Like I said, it’s complicated work being a vomit detective. But I did have one special moment about a half hour before the first of my three hurls. As I was watching television, I noticed the picture go dark. This upset me instantly, because television is pretty important during times of illness. There was little chance I’d be able to fix a modern TV, and I couldn’t go shopping for a new one in my condition.

Before accepting defeat, I took a moment to consider if maybe I had pushed some buttons on the remote by mistake. Maybe there was some setting that turned the screen to black while the audio continued. Maybe I could turn it off and unplug it, then power it back up and it would work again. That’s about the only way to fix the picture on a digital television, right?

As I thought about my options, something occurred to me that I hadn’t considered. There was nothing wrong with the picture on my TV. What had happened was I got tired and closed my eyes without realizing it.

Paul Lundgren is author of The Spowl Ribbon, a book that contains zero stories about vomiting.