PEM or Herx


Senior Member
How do people differentiate between PEM and Herx?

I've always had an issue with all these terms since they seem like just a description of awful reactions to 'something'. Detailed descriptions, but no way to verify what's happening (because we obviously don't understand the underlying mechanisms).

I feel like 'herx' more encompasses that headache feeling I'd get when starting a new antibiotic or something, then it would dissipate and it'd feel better. Or a bit of that feverish feeling, etc.

PEM to me is that delayed poisoned feeling - non-GI nausea and muscle aches and general just awfulness. The only 'remedy' I've found is waiting the hours or days or weeks until it hopefully passes.

But was just trying to take more and more allicin (along with some sophora which I ran out of) since it's one of the few things that makes me feel a bit improved - slightly less brain fog, etc. I thought I was doing okay-ish other than some stomach irritation. Still good digestion overall, perfect bowel movements, etc.

Then a really bad crash after a couple phone calls where they weren't that long and I thought I felt pretty good. Often I'll start feeling acid reflux if I stay on the phone too long, then worse reflux the next day, then migraines, etc. But here I felt totally fine (well, as much as you can feel 'fine' when relatively severe), minimal reflux the next morning and decent HRV numbers. Followed by total bedbound PEM crash.

Was noticing just now along with my PEM nausea and blurry vision, is my neck pain feels 'slightly' improved, which was always one of the benefits I'd get from antibiotics after the initial headache herx. I never had crashes like this, but was more moderate last time I tried antibiotics.

So any thoughts? Nausea, blurry vision and difficulty focusing, exhaustion, poisoned feeling, and so forth. Took no supplements today at all because of the extra nausea, but feeling a slight neck stiffness improvement.

I'm happy to 'fight through' any discomfort or awful feeling if it's doing good, but not sure if the constant allicin stomach irritation is helpful or a sign that I'm taking too much.

(And another reflection back at how surreal all this is - 26 years in and I'm blathering about nothing in some misguided desperate attempt to feel 10% better since doctors are literally worse than useless.)


Senior Member
Thinking further - one of the reasons this doesn't feel like a herx reaction is that I was ramping up allicin over weeks and feeling slightly improved, and then it was just a sudden crash. With antibiotics or allicin in the past, the herx headache feeling would come when I started, then dissipate (although my improvements usually plateaued quickly as well).


Senior Member
Don't know if it will help with your question but I just thought it was interesting back when I found it (and could read it). :)

Thanks for the link!

Highlights issues around the pseudoscience of herxes and PEM and such, but this is what's so frustrating - we're left to these snake oil salesmen because at least they'll admit something might be wrong at all. If we go to 'real' doctors, we just end up with FND diagnoses or hypochondria or at best a meaningless ME/CFS (or LC) diagnosis with zero effective treatment options.

(To be clear - very much appreciate the link! Just when I look at five guys calling themselves Doctor on a medical site and four don't have MDs and one went to medical school in India but they're confident they know exactly the answer...just rubs me the wrong way.)

Never would've imagined living in this world, but I also remind myself I'd likely be pretty dismissive if I weren't actually experiencing this.

Although, I'd be perfectly happy with being a less understanding and less compassionate person who had no experience with ME/CFS and assumed everyone else was just malingering. Being 'understanding' isn't all it's cracked up to be.

Completely off topic and stream of consciousness, but been thinking a lot that I would've much preferred having a healthy but shorter life as opposed to what I got. I never understood that viewpoint when I was younger, or even when I was struggling in the mild-moderate range. I always had an existential dread around mortality, so quantity was even more important than quality.

One 'gift' of this illness is that mortality starts to look like a bit of a benefit.

Ah well, c'est la vie.


Senior Member
How do people differentiate between PEM and Herx?
for me its easy, for me Herx does not exist. originally herxheimer was a reaction to antibiotics due to too much bacteria dieing off at once and releasing toxic substances. but nowadays people say its herx for just every negative side effects, sometimes not making even sense because a bacteria dieoff isnt happening with the substance which was used.
(sometimes i jokeingly say, drinking alcohol results in a herxheimer reaction, it gets bad at first but over time the body adapts... means it must be healthy now).

i just think most is a poisening reaction, body gets too much of a thing he cannot process in a timely manner, he just tries to get rid of it.
most of everything we add to the body, the body needs bound to a protein or convert to some save form. if body cannot make the things save in time, they become toxic.
either they are directly toxic like heavy metals (copper supplementation) or we go from a hypo to a hyper situation and suffer from paradox hyper-x symptoms (like being hypokalemic , and then being hyperkalemic for a short time) or some substance while not in save form acts directly on cells giving signals and directives (like coffein or vitamins).... and sometimes all of them together.

i believe in a CFS state, the body has low capacity of bringing substances into a save form to bring the body back into homeostasis. thats why some get extreme symptoms from low amounts of the stuff we took.
so going slow and ramping up, allows the body to increase capacity for that substance to be handled, like increasing proteins need to bound the stuff or ramp up needed cofactors to handle it.
most can handle vitamins and minerals from foods pretty good. i can eat bananas and potatoes no problems, but when just adding a little bit of potassium powder, i get bad sideeffects. i think this is because of food processing takes much longer and is in much lower quantities.

and of course there are sensitivities to things like sulfur etc. so even foods can make problems. in the end it always comes down to the individuals body what actually is going on.
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Senior Member
I'm doing anti-candida and I definitely get physiological reactions to the herbs and stuff I take, it could just be a feverish immune like response feeling centered in the stomach, a feeling of overall tiredness and sleepyness thats outside of the exertion - PEM - recover cycle of CFS, or it could be feeling cold / sweating / a detox flu like feeling. A tiny pinch of Nu-U CandiAway gave me a sharp spiking localised headache pain the first time I tried it, and a large capsule of just Capryllic acid caused me to develop a new sense of smell towards 'something' for a few hours ( somewhat related to what I call my 'MCS' ), usually i'll pickup these smells that wax and wane from the inside of my respirator, especially if its a few weeks old and its gotten moist inside, I try to keep it dry.


Moderator Resource
Southern California
How do people differentiate between PEM and Herx?
For me, PEM happens like clockwork some 24 hours after over-exertion. The exertion can be physical, mental or even emotional. But the delayed onset reaction is always the same - bodywide aches and exhaustion which generally takes a day to clear due to taking 4000 mg of branched chain amino acids. Prior to starting the BCAAs, my PEM would last 2 - 3 days.

A herx reaction is very real
originally herxheimer was a reaction to antibiotics due to too much bacteria dieing off at once and releasing toxic substances
and that's exactly what it is. Many years ago (pre-ME/CFS) I had severe fatigue after being treated with antibiotics for a bacterial infection and the doctor told me it was a herx reaction, which I'd never heard of before. So I differentiate between PEM, a herx reaction and a detox reaction by seeing what I did (or did not do) prior to hte onset, and if I'd had a bacterial infection that was being treated.

I used to have lots of detox reactions to substances - I believe my body was carrying a rather heavy load of toxins, some of it mercury (lots of fillings as a kid). I'd also had heavy exposure to chemical solvents at a job when I was 19.

I first learned that my general feeling of slight nausea and malaise (using the word properly here, not as the criminally inadequate description of PEM!) was liver toxicity. Also I'd get quite spacey, have trouble concentrating, thinking which I think was from mercury. I ended up having to do a liver detox which helped a lot though I still kept having detox reactions (which I could now recognize by symptoms) to many things - anything which caused a "cleansing" reaction - e.g., cayenne, apple cider vinegar, tons of things.

Eventually I stumbled across a protocol using glycine (caused a severe detox reaction), inositol and glutamine, which I believe got my detox pathways working properly. It took 6 months, and had to start with a very low dose of glycine initially (needed for Phase II liver detoxification) but by the end of the 6 months, my near constant detox reactions stopped. And haven't come back.

My chiropractor who did muscle testing was the one who identified what was going on with toxins. I'm indebted to him for this. He also found my very weak adrenals and helped with that and helped get my digestion system back in order. If I'd never found him and had relied on western doctors for my health, I would be much worse off.

I've recommended muscle testing many times but hardly anyone gives it a shot. It's cheap compared to MDs and for many things much more effective. I've learned to do it on myself, though will see a chiro when I want confirm what I've come up with. For someone just starting it, I strongly recommend you first see a competent practitioner instead of just watching a youtube video. It's deceptively simple appearing.


Senior Member
but nowadays people say its herx for just every negative side effects,
That's my feeling about the term too: so misapplied that it's usually meaningless (just means "feel lousy"). I'm not saying that Herxheimer reactions are fake; just that the genuine ones are probably a few percent of claims of "herx". Thus hapl808's problem of how to reliably identify which "feels lousy" is occurring.

When my ME started, and I had no idea what it was, I tried some anti-candida treatments. They made me feel worse, just like the expected "herx", but it continued with each treatment, with no reduction in the reaction, so I expect it was not due to die-off, but rather some other reaction.


Senior Member
small town midwest
herxheimer was a reaction to antibiotics due to too much bacteria dieing off at once and releasing toxic substances. but nowadays people say its herx for just every negative side effects, sometimes not making even sense because a bacteria dieoff isnt happening with the substance which was used.
This exactly.

A jarisch-herxheimer reaction is a response to death of spirochete bacteria. It only happens when these bacteria are treated with appropriate antibiotics. Most of the time, that means when you are treated for syphilis with a form of penicillin. It is not generally feeling awful after you try a medication. I don't know why "herxing" came to mean any feeling bad after medication, but it's actually a very precise reaction. I think that calling any bad reaction a herx is a problem not just because it's inaccurate so it doesn't help us understand what's going wrong in our bodies, but because it might lull you into taking something that's harmful.

If you are feeling bad after medication, consider:

1) Is this an expected/known side effect?

2) Do the benefits of the medication outweigh side effects?

3) Is this an unexpected reaction that could indicate the medication is hurting you instead of helping?

4) Are you taking the wrong dose? (JHR) is,Lyme disease, and relapsing fever.

Rufous McKinney

Senior Member
but not sure if the constant allicin stomach irritation is helpful or a sign that I'm taking too much.

I got some of the fermented black garlic and take it now and again, and I usually notice some positive effects when I do. Its very mild on the stomach, seems very easy to digest

My chinese herbalist advises me to NEVER take raw garlic, uncooked garlic, or even too much garlic. Despite its many wonderful qualities, in certain bodies, it's very heating.

after the initial headache herx.
I think I have attributed Bubble In Brain to HERX reactions. Unpleasant type of headache. But I'm so intolerant of feeling worse, I don't last long taking anything that causes what might be these reactions.

PEM to me is that delayed poisoned feeling - non-GI nausea and muscle aches and general just awfulness.

Yup. But I"ll lose energy in digestion and that goes off too.

We are so poisoned by something going drip drip, entering our cells, etc.

I got terribly nauseated yesterday afternoon, I felt just HORRIBLY poisoned, but I am also having blood sugar problems, my insulin resistance is much worse, ETCETERA.

edited to add: my BP is not staying controlled well, after beefing up my BP medications substantially.