# Diphenhydramine

Category: Drugs & Compounds

Also known as: Benadryl

Diphenhydramine is an over-the-counter antihistamine that Ray Peat considered useful in specific contexts, primarily for its antiserotonin and antihistamine properties, though he preferred cyproheptadine for long-term reparative effects. Peat noted that histamine activates the…

10 passages · 3 authors · 2019–2026 · Most-cited: [Georgi Dinkov](https://bioenergeticoracle.com/md/voices/georgi-dinkov/index.md)

Canonical page: https://bioenergeticoracle.com/concepts/diphenhydramine

## Synthesis

**Diphenhydramine** is an over-the-counter antihistamine that Ray Peat considered useful in specific contexts, primarily for its **antiserotonin** and **antihistamine** properties, though he preferred *cyproheptadine* for long-term reparative effects. [Source 1, 2] Peat noted that histamine activates the parasympathetic nervous system, which is involved in nausea, explaining diphenhydramine's efficacy against motion sickness. [Source 1] He advised that pure diphenhydramine is better than Benadryl formulations containing excipients, and while he acknowledged its utility, his own experience led him to favor cyproheptadine, which he found had a *reparative effect* allowing for progressively smaller doses until it was no longer needed. [Source 1]

Georgi Dinkov has extensively detailed diphenhydramine's mechanisms, emphasizing that it is a **serotonin antagonist** capable of blocking several 5-HT receptors, including the **5-HT2C receptor** which is the primary controller of ACTH release and HPA axis activation. [Source 5] By blocking this receptor, diphenhydramine can stop the stress response, which Dinkov argues makes it therapeutic for fear-based conditions like generalized anxiety disorder and PTSD. [Source 5] He also notes that diphenhydramine can directly block the **TLR4 receptor**, the receptor for endotoxin, giving it a systemic anti-inflammatory effect beyond the liver. [Source 10] Structurally, Dinkov points out that diphenhydramine is a very close analog of the potent antiviral drug *cinnarizine*, and studies have shown it can block the replication of lethal viruses including Ebola and rabies. [Source 4]

A critical pharmacological caveat raised by Dinkov is that diphenhydramine's effects are **dose-dependent**. In doses below 150mg daily, it acts primarily as a serotonin antagonist, but at higher doses it begins to function as an SSRI, potentially negating many of its benefits. [Source 5] He recommends sticking to a range of 50mg-100mg daily for therapeutic effects, noting that even very low doses—an HED of just 0.15mg/kg, or roughly 10mg-15mg daily—were sufficient to reverse diabetic pathology caused by talc ingestion in animal studies. [Source 5, 6] Dinkov also cautions that older, drowsiness-inducing antihistamines like diphenhydramine tend to be safer than newer non-drowsy formulations, which often contain halogenated atoms like chlorine or fluorine that can have **liver toxic effects**. [Source 8]

Danny Roddy has contextualized diphenhydramine as a secondary tool for managing symptoms arising from a deeper metabolic problem, noting that any low-thyroid condition will destabilize mast cells and release more histamine. [Source 3] He observed that Peat was somewhat vague about the drug, suggesting it was not a frontline recommendation but could be good in small amounts. [Source 3] Roddy also relayed that some individuals, including himself, experienced significant side effects from related antiserotonin drugs like cyproheptadine, such as profound next-day fatigue and nightmares, which Peat attributed to the drug's effect on **acetylcholine**. [Source 7] Dinkov has recommended diphenhydramine as a practical over-the-counter option for emergency preparedness, ranking it alongside antibiotics and thyroid as a crucial drug to have on hand due to its antiserotonin and anti-inflammatory effects. [Source 9]

## People also ask

### How does diphenhydramine block the stress response?

Georgi Dinkov explained that diphenhydramine acts as a serotonin antagonist, blocking the 5-HT2C receptor which is the primary controller of ACTH release and HPA axis activation, thereby stopping the stress response.

### Why is the dosage of diphenhydramine important for its effects?

Dinkov noted that diphenhydramine's effects are dose-dependent; below 150mg daily it acts as a serotonin antagonist, but at higher doses it functions as an SSRI, so he recommends 50mg-100mg daily for therapeutic benefits.

### How does diphenhydramine compare to cyproheptadine in Ray Peat's view?

Peat considered diphenhydramine useful for its antiserotonin and antihistamine properties but preferred cyproheptadine for long-term use, as he found it had a reparative effect allowing for progressively smaller doses.

## Related concepts

- [Anemia](https://bioenergeticoracle.com/md/concepts/anemia/index.md)
- [Crabtree effect](https://bioenergeticoracle.com/md/concepts/crabtree-effect/index.md)
- [Estrogen-serotonin axis](https://bioenergeticoracle.com/md/concepts/estrogen-serotonin-axis/index.md)
- [Famotidine](https://bioenergeticoracle.com/md/concepts/famotidine/index.md)
- [PCOS](https://bioenergeticoracle.com/md/concepts/pcos/index.md)
- [Tetracycline](https://bioenergeticoracle.com/md/concepts/tetracycline/index.md)

## Cited passages

Passage numbers match the `[Source N]` markers in the synthesis above.

### Source 1 — Ray Peat Email Advice Depository — Post 865

Ray Peat · Email · Dec 3, 2022

> [Sat, Mar 19, 1:10 AM]
>
> **Question:** Hello Dr. Peat When I increase my fruit and cheese consumption I usually get motion sick quite often and tonight I wondered why for the first time. I started reading about the drug that always helped me in these situations since I was a kid. The main ingredient of the drug is diphenhydramine - an antihistamine - which is also one of the main ingredients of benadryl. Do you know if diphenhydramine is a safe thing to consume on a daily basis or at least several times a week in order to keep my histamine under control and what is the mechanism of action there - why would antihistamine help me with motion sickness? Much love
>
> **Ray Peat:** Histamine activates the parasympathetic nervous system, which is involved in nausea. Pure diphenhydramine is better than Benadryl. Cyproheptadine is another antihistamine. Histamine supports wakefulness, and too little lowers alertness.
>
> **Question:** Thank you Dr. Peat Do you think Cyproheptadine would be safer than diphenhydramine? Would the minimal those of these substances be safe to use long term?
>
> **Ray Peat:** My experience has been that cyproheptadine had a reparative effect, so that after a few days using a milligram, a half or fourth worked as well, and then I didn’t need it again for a long time.

### Source 2 — #57: Fasting, Depression, and Serotonin | The Obesity Paradox | Psyop Overload | Acid Reflux with Georgi Dinkov

Georgi Dinkov · Interview · May 16, 2021 · https://open.spotify.com/episode/5EowLKmTLLWkK392oxil5W

> **Georgi Dinkov:** Myanserin, also known as mirtazapine. But all of these are by prescription only. So your best bets for over-the-counter would be diphenhydramine, also known as Benadryl, and phobotidine. And then, of course, a variety of other anti-serotonin. A variety of the chemicals that we're discussing here have anti-serotonin effects, like pregnenolone, progesterone, aspirin, especially DHEA. The studies going back to the 1940s demonstrate that whenever the amount of androgens in males, at least, in the body rises, the whole serotonin system gets kind of quieted down. Its effects and activity get suppressed. And that may be one of the reasons why androgens have known antidepressant effect in both men and women. So if you can get access to antiserotonin chemicals, you know, I guess the steroids, the ones that are available are your second best bet.

### Source 3 — Bioenergetic Helpline #3: Fifty Cups of Coffee Per Day, Fat Malabsorption, Reverse T3, Mushrooms

Danny Roddy · Interview · Dec 13, 2025 · https://www.youtube.com/watch?v=PXS_hNS3uis

> **Danny Roddy:** benadryl and a friend of mine had found like a clean version on amazon i can't recall what the name is but maybe i can post it in the show notes and
>
> **Caller:** um you can finish that
>
> **Danny Roddy:** well that's all i had to say
>
> **Caller:** Okay. Yeah. So I think that some symptoms I've had since childhood were related to histamine and serotonin. So this past summer I started experimenting with some things like that. And I found what I thought was a clean Benadryl. It was a brand for like children's allergy medicine called like Genexa.
>
> **Danny Roddy:** I think that's it. Yeah.
>
> **Caller:** yeah and that one's just like the diphenhydramine with um i don't know water uh like citrus flavoring but the base was like a agave syrup uh lowering stress helping sleep uh stopping uh like obviously histamine symptoms like uh you know itchiness of the skin and things like that That was something that I've heard Ray mentioned people, people have asked him the past and he I always thought he was kind of vague about it. Obviously, it wasn't something that he thought was like a frontline thing. But he said it was maybe good in small amounts.

### Source 4 — #21: Coronavirus, Hair Loss, Finasteride, DHEA, DHT, and Question Catch-Up with Georgi Dinkov

Georgi Dinkov · Interview · Mar 27, 2020 · https://open.spotify.com/episode/2tym7r7CIbtrzBp8EMoX7S

> **Georgi Dinkov:** If also other things that can be done that are over the counter, but there happen to be drugs, the antihistamine Benadryl probably could help. It's been shown that, first of all, that antihistamine also has antiserotonin effects. And it has been shown in a number of different studies to be able to block the replication and the infection, even with some lethal viruses like Ebola, rabies, and even HIV. Now, whether you agree that HIV is a lethal virus or not is a separate story, but Benadryl was successfully used in at least three separate studies. And structurally, Benadryl is very similar to the anti-serotonin drug Sinacerin, which Ray mentioned on a few recent interviews. And Sinacerin is known to be able to stop the development of COVID-19 and potentially cure it. So it can both prevent and cure it. Unfortunately, it's not available directly, but diphenhydramine, which is the chemical name of Benadryl, is structurally very closely, is a very close structural analog and potentially has similar effects.

### Source 5 — Serotonin (5-HT) drives fear and conditions such as anxiety/PTSD

Georgi Dinkov · Article · Dec 16, 2022 · https://haidut.me/?p=2080

> Conversely, blocking 5-HT or lowering its synthesis can probably cure most fear-based conditions such as generalized anxiety disorder (GAD), PTSD, psychotic conditions (e.g. schizophrenia), etc. At least, those are the findings of the study below, which demonstrated that animals completely lacking the 5-HT2C receptor were absolutely fearless and impervious to the development of anxiety and stress-driven pathologies. Interestingly enough, the 5-HT2C receptor is the primary controller of ACTH release, and thus the activation of the HPA axis. In other words, activating 5-HT2C (which serotonin does) activates the stress system, while blocking it stops the stress response. Even more interestingly, many SSRI drugs (and especially Prozac) are antagonists of the 5-HT2C receptor, which probably explains most of their antidepressant effects.
>
> [references]
>
> In other words, chronic stress drives conditions such as depression, anxiety and PTSD through the HPA axis, and blocking the HPA system or its master regulator 5-HT has therapeutic effects for those conditions. One of the most widely-available serotonin antagonists is cyproheptadine and it has already been shown to stop the nightmares of people diagnosed with PTSD. Other serotonin antagonists capable of blocking 5-HT2C include metergoline, the tricyclic class of antidepressants, and the OTC chemical Benadryl. Yes, diphenhydramine (commercially sold as Benadryl) is an antagonist on several 5-HT receptors. Word of caution for Benadryl – in doses below 150mg daily it has mostly 5-HT antagonism effects, but in higher doses it starts to act as an SSRI so many/most of its benefits may be negated. Thus, if Benadryl is used I’d stick to doses in the 50mg-100mg daily range, which have already been shown to have therapeutic effects in conditions such as diabetes, so we know the lower doses are effective and there is no need for taking the higher doses that many doctors and pharma companies push for financial reasons (i.e. higher doses = more money spent).
>
> And now, as per the study below, it looks like blocking those pathways can also prevent those conditions.

### Source 6 — Even a tiny amount of talc may cause diabetes II (T2DM), Benadryl may reverse it

Georgi Dinkov · Article · Aug 27, 2019 · https://haidut.me/?p=500

> As many of my readers know, talc was recently implicated as an (ovarian) carcinogen. There have been several class-action lawsuits against manufacturers of baby powder containing talk and the ones that have reached verdicts already all found the talc vendors culpable.
>
> [references]
>
> However, the amount of talc applied to body by users of baby powder is rather large, usually at least several grams per application, and powder vendors have repeatedly stated that when used in amounts under a gram talc is completely safe. The study below begs to disagree. It demonstrates that even a tiny amount (HED 1.5mg/kg) of talk ingested on a daily basis reliably causes diabetes II (T2DM) in just 2-3 weeks. This amount of talc exposure can be achieved with taking just 1-2 pills of most prescription drugs as talc is used as an excipient in most pharma drugs. That means many cases of T2DM are actually iatrogenic in origin as most people in US take at least one prescription drug daily. The good news is that even a low-dose Benadryl (diphenhydramine) was able to reverse most of the diabetic pathology caused by the talc in just 3 weeks. The HED of Benadryl used in the study was 0.15mg/kg daily, which means that for most people 10mg-15mg daily would be enough to replicate the study design. Since most Benadryl formulations on the market contain at least 25mg per pill, it should be very easy (and cheap) to contain the damage caused by talc. In addition, there are other studies demonstrating anti-cancer effects of Benadryl, so this humble chemical may even be able to contain the carcinogenic damage caused by the excipient.
>
> [references]

### Source 7 — Bioenergetic Helpline #7: Synchronicity, Adrenaline, Anemia, Cyproheptadine, Financial Reset, Mexico

Danny Roddy · Interview · Jan 9, 2026 · https://www.youtube.com/watch?v=9yCh9ZsqRDo

> **Caller:** okay one more question um about uh separate hypodyne um so what what is there any like uh idea if if a person has high sensitivity to it like um you know taking like a quarter of a milligram and then next day feeling like very tired and like basically dull like you know
>
> **Danny Roddy:** That's generally probably good. Like I don't think you want to be insensitive to it I think that would mean the stress was extremely high for what it's worth I think in 2017 I tried to take a quarter of it every single day and I was having a hard time not feeling completely bonked out the next day and Around that time it was one of my like book investigation calls to write You and i told him that and he said some people just don't do well on it like and he he had uh said something that people could get really bad nightmares on it and that was happening to me as well and so i just at that point and also my mouth was kind of drying out and he had also said that could be a consequence of it and so again i'm not trying to scare anybody like i i hardly ever hear this happening but that did happen to me and so i i really haven't taken it much since then but yes for some people i guess it just doesn't work very well

### Source 8 — The ThermoDiet Podcast Episode 124 - Georgi Dinkov

Georgi Dinkov · Interview · Feb 19, 2023 · https://www.youtube.com/watch?v=4aRyulc5-RM

> **Thermo Diet:** That was my next question. You read my mind. Is there anything wrong with using the more potent hanaistamines, like what is Benadryl? It's diphenhydramine.
>
> **Georgi Dinkov:** Diphenhydramine, yeah.
>
> **Thermo Diet:** Diphenhydramine. Is there anything wrong with using that relatively consistently, or is there anything you'd want to take with that?

### Source 9 — #57: Fasting, Depression, and Serotonin | The Obesity Paradox | Psyop Overload | Acid Reflux with Georgi Dinkov

Georgi Dinkov · Interview · May 16, 2021 · https://open.spotify.com/episode/5EowLKmTLLWkK392oxil5W

> **Danny Roddy:** Awesome. I'm going to hang up on you, Lucas, but thank you so much.
>
> **Caller:** Awesome.
>
> **Danny Roddy:** Okay, take care, brother. I think it affects the sound quality a little bit, so that's why I did that. But go ahead, George.
>
> **Georgi Dinkov:** I mean, so the ones that are available, you can buy the ones that I just, as I kind of mentioned, as part of the prepping thing. Benadryl, I think the chemical name is diphenhydramine. And some of the, so the anti-acid drug famotidine turns out to be a potent serotonin depleter or antagonist. We don't know yet, but it was capable of stopping a full-blown serotonin syndrome, which would have probably killed the person because once it really gets severe, like an acute severe serotonin syndrome, about 40% of people die. So famotidine was injected at a dosage of 20 milligrams and immediately stopped it, which even cyproheptadine sometimes struggles to do. And there are older studies showing that because famotidine is an antagonist of the histamine 2 receptor, which people thought was mostly expressed in the gut, but it turns out it's also expressed in the brain and blocking that receptor apparently has some kind of a feedback mechanism. And it lowers the production of serotonin in both the brain and peripherally. That's my explanation. It could also be a serotonin antagonist like cyproheptadine, but I suspect the more likely version is famotidine actually acts similar to a TPH inhibitor because it decreases the synthesis of serotonin. And it's available over the counter in most countries. The only problem is if you're buying the commercial version, which comes in a pill, it usually comes with some not very nice excipients like talc and titanium dioxide and sometimes silica and sometimes some artificial colors. You know, it's not ideal, but if that's your only option, it's probably better than nothing, especially if you're dealing with severe serotonin issues or society is collapsing. And then other things you can do, other anti-serotonin, but they're usually by prescription only, are the older tricyclic antidepressants, such as nortriptyline, amitriptyline. And some of the reincarnations, such as myanserin, which I think is available in Australia.

### Source 10 — Thermo Diet Podcast Episode 39 - Georgi Dinkov

Georgi Dinkov · Interview · Jul 19, 2020 · https://www.youtube.com/watch?v=11N-wEMl_Ks

> **Georgi Dinkov:** It's marketed as a drug for allergies, but older studies in the 60s and 70s found... this drug can actually directly block the tlr4 receptor so so you know basically the idea the preferable thing is to start as early as possible in the cascade which is what the charcoal and the soluble fiber and the the medium chain saturated fatty acids will do once it gets to the liver then the goal should be controlling inflammation and supporting the liver as much as possible with nutrients which means right? Because the liver consumes a lot of glycogen in trying to get rid of this endotoxin. So the anti-inflammatory substances, making sure glycogen stores are high, avoiding the polyunsaturated fats because they are actually precursors to the inflammatory mediators known as prostaglandins and leukotrienes. So if you're ingesting a lot of PUFA in your diet together with ingredients that feed the bacteria. So in other words, if both PUFA and endotoxin make it to your liver, then it's really like a much worse situation because endotoxin activates the enzymes. cyclooxygenase, and lipoxygenase. And those family of enzymes synthesize potent inflammatory mediators from the PUFA. So you're giving yourself like a double whammy of an inflammation attack by consuming PUFA and foods that feed off this endotoxin reaction. So yeah, the drugs Benadryl. And the good thing about them is that they act not only on the liver, but systemically as well. And then anti-serotonin chemicals like cyprohepatidine are also very important. Methylene blue, because it's probably the most potent anti-nitric oxide agent that we have as over-the-counter, it both neutralizes already existing nitric oxide in the blood and also inhibits its synthesis by reducing the expression of the enzyme known as INOS.

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