Mental Effects of Antihistamines Anxiety Insomnia Depression

Mental Side Effects of Antihistamines

In Antihistamine Addiction, Symptoms by Anthony2 Comments

Mental Effects of Antihistamines Anxiety Insomnia DepressionAntihistamines Causing Anxiety, Depression, Headaches and Insomnia

I’ve had allergies for a long time now and they had been especially bad during my teenage years. During that time, I was heavily dosed up on antihistamines like Zyrtec, Bendaryl, and Allegra to cope with the allergy symptoms.

I have experimented with a lot of different allergy drugs because my symptoms were so severe and I had noticed some peculiar side effects that didn’t really make sense to me. Nobody, including my doctor, told me that I would experience uncomfortable mental side effects like anxiety, depression and insomnia. Let me share my experiences with you about how antihistamines affected me mentally and some research that supports how some people claim to also have these adverse effects.

Do Antihistamines Treat or Cause Anxiety?

This subject is a little bit of an oxymoron because antihistamines may treat anxiety, but they may also cause the same thing that they’re treating. I think this is true for most medications when they are administered for long-term use.

The antihistamine drugs available over-the-counter and via prescription were all chemically derived from antidepressants and SSRI’s. Doctors know this and they often tell their allergy patients that the medication may soothe their anxiety as well. In fact, many patients have reported that they don’t have allergies, but they were prescribed an antihistamine to treat their anxiety instead.

Because this is still happening to this day, I wonder how this makes any amount of sense because there are so many better treatments for anxiety. I could think of a few off the top of my head: green tea, fish oil, anxiety medication maybe? This leads me to believe that the pharmaceutical companies are saturated with bribe money going to doctors. There’s evidence to suggest that the companies who own antihistamines convince researchers to conclude their studies by saying that antihistamines may benefit all of these conditions, while they ignore the possible long-term effects on the nervous system and immune system.

Personally, I do not trust the research about prescription and OTC drugs because of the fact that money is so heavily involved in the process.

Why I also don’t trust most of this research is because of my own personal experiences with these drugs. I know for certain that I had withdrawal effects from Allegra, Zyrtec, and Benadryl.

Benadryl Mental Side Effects Headache Insomnia Anxiety Depression

Benadryl Affects the Nervous System and Sleep Pathways

I first took Benadryl when I was a child to help with my allergies and my sleep, as well as my allergies during sleep. If you’ve ever taken it before, you’d know that this drug definitely has effects on the nervous system. Diphenhydramine is an anticholinergic drug that interferes with the chemical action of acetylcholine, which is important for movement all over your body. This also accurately explains why this drug can impeed your ability to form memories and keep older ones.

Benadryl also has an effect on GABA in your brain, which is the stuff that’s in higher amounts when you drink alcohol. GABA can be seen as the drowsiness neurotransmitter because it signals your brain that you haven’t gotten sleep and that you need it. Therefore, the side effects of this antihistamine stem from restricting muscular movement (controllable and uncontrollable like your heartbeat) and increasing the sleep signals in your brain.

That right there is definite proof that some antihistamines have the ability to affect you mentally and physically. However, another point that must be made is the long-term effect that this has on your health. As with most drugs and substances, if you take Benadryl for a long period of time, you may experience withdrawal symptoms if you suddenly stop taking it cold turkey.

We pretty much know exactly how antihistamine withdrawal works, which can be associated with one of the effects of Benadryl. Antihistamines work by blocking histamine release by quickly excreting it from your body as it is being produced. The bad part about these drugs is that your immune system does not recognize the mechanism of what is happening, so it produces more and more histamine in response to the same allergen it is exposed to.

Diphenhydramine Causes Mental and Physical Withdrawal

So your immune system is pushing more and more histamine out each day, but every day the antihistamine is getting rid of it. After 100 days of this, you’ll stop taking the Benadryl and experience an influx of huge amounts of histamine that your body has been trying to push out. This can be classified as antihistamine withdrawal due to its effects on histamine alone.

You also need to consider the other physical actions this medication has on your body, like the anticholinergic and drowsy-producing effects I described. Your body can experience a type of withdrawal from these mechanisms as well. After 100 anecdotal days of straight taking Benadryl to deal with your allergies or insomnia, you could experience nervous system and mentally related symptoms as your body recovers from the drug.

This is where Benadryl causes the exact conditions it was supposed to treat, just like allergies. After you stop taking it cold-turkey, it will be much harder for you to fall asleep and concentrate. Since your body physically relied on this substance to help it fall asleep, it will expect Benadryl again at bed time because animals have evolved homeostasis and adaptation to its environment. If you’ve ever gone through a similar experience with stopping Benadryl, you know too well that insomnia is to come during the night. Levels of GABA will be decreased at the appropriate times, leaving you tossing and turning even if you physically exerted yourself during the day.

If the duration and dose of Benadryl is higher for an individual, these withdrawal symptoms will be more pronounced. The effects on the nervous system will also be apparent. During the Benadryl withdrawal, I personally experienced killer headaches, sea-sickness and lights flashing in my peripheral vision. This may be due to the drug withdrawal itself or the fact that my sleep duration and quality was dramatically decreased during this time. I directly attributed this to the drug.

You can read more in-depth about my withdrawal from Diphenhydramine here.

Zyrtec Mental Effects Antihistamine Irritability Itching Anxiety Depression Mood

Irritability and Anxiety With Zyrtec

After I decided to stop taking Benadryl, I started Zyrtec to try to deal with the withdrawal effects because they were just unbearable. My doctor had recommended that I substitute with another OTC antihistamine for some reason that didn’t make sense to me. I tried it and it seemed to work much better than Benadryl overall with a little bit less drowsiness.

Zyrtec brought with it a different set of mental side effects that got worse and worse down the line. I think that I took Zyrtec for about 1 year and that was 1 year too long.

While I was on it, I remember being much more irritable and easily agitated by the most simple things for no good reason at all. Usually, the irritability would start about 6 hours after I took the medication. The first six hours had like a calming, antidepressant effect that went nicely with the antihistamine effects. It felt good to quickly be free from allergy symptoms, but the ride always took a turn for the worst. At least this was the case for me.

Antihistamine Drugs Cause You To Crash Later

For the first couple of months, I didn’t even attribute the increased anxiety and agitation to coming down off of the effects of Zyrtec. I thought that it was because I had mental problems of my own that I had to deal with, which may or may not have been caused by my diet and lifestyle. I tried to improve my diet and exercise more, but I was still irritated by dumb things on Zyrtec.

Reading about other people’s experiences with Zyrtec, it seems that it definitely has mental side effects that some don’t even notice.

Strictly speaking about the mental side effects of Zyrtec rather than the physical effects, I think that this drug is very suspicious and risky to take. I think that it may even be dangerous for children to take because they are in such a critical phase of development. Looking back in retrospect, as an adult taking Zyrtec, it had such powerful effects on my mental health that I am now afraid of.

Of course, I still consider that everybody is different in their unique state of health and genetics. Some people may be more susceptible to certain symptoms as opposed to others who may find that Zyrtec actually does work well for them. However, I have heard far more horror stories than good ones. In fact, I haven’t heard anything good about Zyrtec in a while.

Zyrtec Also Causes Unbearable Itching and Burning Sensations

Then, we can talk about the physical effects that Zyrtec can have on your body. The most notable effect that users typically think of first is the unbearable itching associated with Zyrtec withdrawal. After you stop taking this drug, it causes an annoying itching sensation all over your skin, which is coupled with the intensified allergy symptoms and irritability. We should be considering this OTC antihistamine as an addictive substance because its use typically results in a recipe for disaster of symptoms. In my opinion, it’s just not worth it to take Zyrtec for your allergies because of the long-term effects.

The itching side effects are caused by the influx of histamine when you stop taking the drug. It’s part of the withdrawal.

Read more in-depth about the long term use of Zyrtec and its withdrawal symptoms here.

Allegra Mental Effects Headache Motivation Hallucinations Insomnia Nightmares

Headaches and Hallucinations With Allegra

I only took Allegra for about 3 months, but that was more than enough time to experience side effects and withdrawal symptoms. In my experience, Allegra worked better than both Zyrtec and Benadryl for my allergies and it also had side effects that weren’t as bad.

The first month of taking Allegra was fine because it seemed to be working effectively for my allergy symptoms and for a longer duration. However, I was beholden to this drug because my immune system relied on it so heavily.

If I didn’t take an Allegra each morning, my allergy symptoms would come back with a punch even if the pollen counts weren’t very high. This always made me reach for the bottle. So I can say from my experience that this antihistamine was addictive and that it directly causes the allergy symptoms it is supposed to treat.

This Antihistamine Also Messed Up My Brain

After two months of taking it, I was tired of yet another cycle of abuse with another OTC antihistamine drug. I stopped taking it and immediately experienced withdrawal symptoms. Of course, the allergies came back with a kick, but the mental side effects were pronounced even more so than Zyrtec and Benadryl.

The withdrawal from Allegra gave me killer headaches and migraines throughout the day to the point where I couldn’t be functional or productive. It gave me some sort of bad trip psychedelic experience too because I would hallucinate and see shadow people in my peripheral vision. My dreams also reflected this because the withdrawal would give me trippy nightmares.

Allegra didn’t particularly affect me physically, but the mental effects were more pronounced. I didn’t have much trouble falling asleep personally, but the nightmares were pretty trippy.

Read more about Allegra withdrawal here.

Mental Side Effects Are Caused By Histamine Fluctuations and Inflammation

I associate the mental withdrawal effects from OTC antihistamine drugs with its effects on histamine and the immune system. Histamine has widespread effects on the body because of its ability to produce inflammation. That’s the point of this chemical in the first place. It was evolved by animals as a way to target self-inflicted inflammation wherever it needed to. Inflammation was useful in the wild to physically kill pathogens, parasites, and other types of invaders.

I believe that researchers around the world should begin studies to understand more about the effects of histamine in the body and especially on the brain. We know for certain that histamine does something to the brain, which you can deduce that antihistamines do as well. Western doctors must have some sort of clue because a lot of them prescribe OTC antihistamines to patients that claim to have mild to moderate anxiety. They may have learned that antihistamines were originally derived from antidepressant and anxiety medications.

Natural Antihistamines Don’t Have Negative Effects on the Brain

This brings me to my savior point, which completely solved my allergy problem and addiction to OTC drugs. I had always believed in a more natural lifestyle that tried to heal my health conditions organically, rather than mask the symptoms. Because masking symptoms like antihistamine drugs do just increases the problem for the long-term, they directly cause the allergies that they are trying to treat.

Natural antihistamines are different, though. If you have never tried one, I would suggest that you DO IT PLEASE and try to replace it with your OTC antihistamine like Zyrtec. They have little to no side effects and they actually have side BENEFITS that are completely the opposite of antihistamine side effects.

The natural antihistamine that I recommend is quercetin, which is the compound found in onions, fruits and vegetables that gives them that beautiful silver color. Quercetin is derived from food sources, rather than artificial compounds, so your body can process and absorb it more efficiently.

I’ve tried a lot of quercetin supplements that didn’t have much effect on me, probably because the dose and quality were not high enough. Then, I tried this supplement on Amazon and it changed my life forever. It’s a natural allergy supplement that incorporates quercetin and bromelain, an allergy enzyme that helps to break down histamine rather than block it.

Organic quercetin and bromelain antihistamine

The best quercetin supplement that I’ve tried. It includes bromelain, an allergy enzyme.

Natural Allergy Supplements Are More Effective, Cheaper and Healthier

This works to treat and heal the root causes of allergies because it still allows your immune system to release histamine. But after it does, the quercetin and enzymes break it down so your body doesn’t get confused like “why isn’t the histamine coming out? Okay let’s make more and more to solve the problem.”

Therefore, quercetin is not addictive at all. In addition to the effective benefits for allergies, quercetin has positive effects on your brain. Quercetin is an ingredient that is recently starting to be added to energy drinks and supplements like Monster because of its natural ability to enhance cognitive function, positive mood and focus. I think that’s great because they are using harmless natural ingredients rather than artificial stimulants that could cause heart failure or something.

When I take this quercetin supplement, not only do I not have any allergy symptoms at all, but my mood and motivation is increased as well for about 6 hours. There is no crash afterwards like with Zyrtec or stimulants like coffee.

In addition to that, this supplement has bromelain, which also has benefits for digestion. I have noticed that my digestion and bowel movements have also improved tremendously.

I love quercetin with bromelain because of how it actually treats my health, rather than masks symptoms and causes more side effects.


If you have a question or something to add about the mental effects of antihistamines, please leave me a comment below!

Talk to you soon,


Mental Side Effects of Antihistamines was last modified: November 8th, 2018 by Anthony


  1. Hi there, Anthony!

    Thank you for sharing your personal experiences, as well as your research and interpretations on the studies! I’m about to graduate from Lee University with a bachelor’s in Psychology, and did a lot of undergraduate research with one of my favorite professors. Research was definitely my favorite part of undergrad, to say the least.

    I don’t know a lot about allergy research, so your blog has helped catch me up on a ton of things that I didn’t really know about. I feel like I’m in the same boat as you were in, and am going to ask for some specific advice.

    I’m currently taking levoceterizine (Xyzal), and have been for 2 years now. I use flonase and eye drops as needed since these allergies are year-around and pretty severe. I used to get sinus infections ALL the time before I started taking it, and since I began taking it daily, the sinus infections have stopped! However, I feel more cloudy and have trouble paying attention to details sometimes. While that could be related to personality, sleeping/eating/exercising habits, and so on, I’m more skeptical of OTC allergy meds since I began reading about the effects of anticholinergic meds on the brain, and I’m convinced that the allergy meds been effecting my mental health as well. I’ve struggled with feeling foggy, having hearing delays, and with paying attention, which makes me feel like there are some cognitive effects to allergy medicines, although that could be a hunch. I’ve also struggled with anxiety and depression my entire life, but haven’t been medicated for that until the last 3 months. I’m now taking a small dosage of eslacitopram (Lexapro) daily until I can figure out what the next step should be.

    I’ve never considered herbal allergy supplements until after reading your blog, but I just bought the 40-capsule bottle of the Allurtica that you suggested, and am hoping for the best.

    What is your advice for this situation? Should I take the risk of getting sick and completely stop taking the Xyzal once the herbal supplements come in? Is finding the right herbal supplement like a trial-and-error gamble, like most medicine can be? Do different combinations of these supplements help people differently, depending on their body types? And lastly, do you feel like Xyzal had any mental effects on you (if you’ve taken it)?

    Thank you for your time!

    -Hannah Adkins

    P.S. If you know your Myers-Briggs personality type, you should totally include it in your response, just for my curiosity. My research professor says that it’s a bunch of bull, but to each his own. 😉

    1. Author

      Oh wow then that supplement is going to really rock your world. Because that stuff is so much better than any OTC antihistamine and it actually makes you feel uplifted. I think it should completely kick you off the other stuff just like it did for me. Let me know! Thanks a for coming and sharing your experience!

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