Cannabis for allergies, etc— there’s a risk re viruses;
(and this might be true of antihistamines, too.)

Russell Irvin Johnston
5 min readDec 6, 2018


by Russell Johnston
December 6, 2018

If allergies (say MCAS — mast cell activation syndrome) are a big problem for you, the benefits of cannabinoids are clear. To quote a 2017 article:

“ Cannabinoids are profoundly anti-inflammatory and impair many Ca2+-dependent enzyme systems which are central to inflammatory and cell-autonomous antiviral responses.”

But notice the sting in the tail of that sentence? The abstract goes on to spell it out:

“ In all other virus infections, both in vitro and in vivo, cannabinoid treatment led to disease progression, increased pathology, and sometimes to host death.”

Of course, they aren’t saying, and I am not saying, that that’s the common case. But it is possible. Just bear in mind that cannabis has risks, as nearly every common allopathic drugs have. There’s a big upside for those of us with allergies or other inflammatory illnesses, yes; but a big possible downside, too.

But it shouldn’t be assumed that these risks are restricted to cannabis: the alternative treatments, such as H1 and H2 antihistamines, may well pose similar risks.

Just before I get to that: I want to interject that evidence is accumulating that either cannabis products or antihistamines (including antidepressants, which are very strong antihistamines) reduce brain inflammation; and that’s getting much attention recently as a cause of both “brain fog” and mental illness, for example:

Mast cells in neuroinflammation and brain disorders.


Neuroinflammation, Mast Cells, and Glia: Dangerous Liaisons

So make no mistake, the reasons to take either cannabinoids or antihistamines can be very strong ones, for many of us. (Brain fog and allergies definitely go together.)

As for antihistamine and viral risks; first the good news — some have (at least narrow) antiviral properties:

Curcumin inhibits hepatitis B virus infection by down-regulating cccDNA-bound histone acetylation.


The Antihistamine Drugs Carbinoxamine Maleate and Chlorpheniramine Maleate Exhibit Potent Antiviral Activity Against a Broad Spectrum of Influenza Viruses.

Now the bad news. Mast cells are a big part of our response to pathogens (infection) and histamine is a master hormone that affects an amazing number of processes in the body, which mast cells release. So it shouldn’t be surprising if antihistamines pose a similar risk to cannabinoids, namely a risk that by dampening down the body’s immune response, we risk letting a virus (or something else) run wild. Nobody’s saying that’s likely, but it’s a risk. Not enough is known about just how much of a risk we are running by taking antihistamines, but here’s an expression of the concern, re H2 antihistamines (such as ranitidine):

Acid-Suppressive Therapy and Risk of Infections: Pros and Cons.

Unfortunately, I have to leave you without being able to draw a firm conclusion about these risks re antihistamines — even whether they exist at all — and whether you should run them.

As for myself, I dropped antihistamines a couple of years ago to get a tan (antihistamines block melanin formation, which is to say, tanning.) Although they might have helped me back then, I never started (in recent decades, at least) on cannabis or cannabinoids for allergies — except for the endocannabinoids we get with lots of total darkness at regular times, at night. Those, I get a lot of!

Right now I’m exploring a different avenue, of stopping MCAS at the source by finding out what really triggers it; and getting a remission from it. Some say there’s no such thing, but I’ve experienced rare remissions before, and this year, I’ve experienced two remissions of maybe a couple months each.

Some recent tomfoolery experimenting with my health (seeing what I could get away with, I suppose) knocked me off my perch a month ago, and landed me back in MCAS-land, sadly. But I expect to be back in remission by the New Year, because I’m optimistic enough to think that I’ve finally identified four modern lifestyle factors that — together — cause MCAS and can therefore remove it, too. Tanning (plus UV) is one of those four factors. But not the biggest one, if I’m right. Wish me luck!

The Cannabis Wars

Not long ago, if cannabis was the one drug that best countered your MCAS and related symptoms, say by far, you were likely to be attacked even for mentioning that in online forums. Too often the topic was censored or removed altogether from forums. The world has changed, and MCAS patients are, overall, better off for that, I feel sure. But the energy of that debate — on both sides-still pops up sometimes.

Which may explain a few objections I’ve received, saying that this story is fear-mongering, by mentioning any side effects of marijuana or its derivates at all. There was a time. Within memory, misleading government-sponsored, peer-reviewed journal-published research that was only designed to fear monger vs cannabis was being publilshed. “Research” that was not accurate, balanced, or well done. I hope that day has passed, and don’t have any reason to suspect the article I’ve cited. Then again, I live in a jurisdiction (Canada) where the war is over and cannabis (licensed) is the law of the land, now. So it’s easy for me to forget that elsewhere, that war goes on, and intransigent governments and perhaps medical societies still exist.

Neither I or the cited journal article say you shouldn’t take cannabis.

Trade Offs

The body is an economy, and everything affects everything. For example, in MS, it’s common to damp down the immune system heavily with drugs. But it’s also well-known that deaths from infection rise when you do this. It’s a balance that has to be taken into consideration when prescribing, including prescribing for yourself.

One should expect anything that strongly reduces the activity of the innate immune system also impairs the innate immune system because that’s pretty much what the words mean. A long, exhausting run also impairs innate immune system function briefly because the body other work is more important, for the moment. So does ketosis, and that also has both good and bad effects.

If you don’t happen on a tough bug, no problem. If you do, the basic purpose of much of the innate immune system to slow all infections down a little as soon as possible, in order to give the adaptive immune system time (maybe three days) to kick in. Sometimes, the short head-start that the innate immune system gives to your adaptive immune system (antibodies etc) really matters. Mostly it doesn’t. So again, it’s a balance. Our symptoms are severe, and can be life-threatening, so taking small risks is justified: but that’s no reason to refuse to learn about side-effects. It’s better to know.

Drugs always have consequences to be weighed. For aspirin, it’s bleeding, and that can kill ya. It’s not fear-mongering to warn people who like NSAIDs to look for signs of bleeding in their stools.

I’m unaware of any drug with no side effects. I use salt as a drug for dysautonomia, and it has side effects in large doses. It would be very unreasonable to expect marijuana or its derivatives to be that one drug that has no side effects. If that’s your view, and you can support it, I’d be very glad to look at the evidence.

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Russell Irvin Johnston

I've read at least the abstracts of (far) more than 250,000 peer-reviewed medical articles, I studied the history and philosophy of science at University.