Do antihistamines (allergy meds) make you fat or affect exercise performance?

Posted on October 31, 2012

(Last Updated On: April 11, 2016)
allergy meds exercise

As usual, it depends.

For the first 23 years of my life I never had a single allergy. In fact, I used to vehemently make fun of those who did. Words such as “genetically inferior” would get thrown around.

Then last year I had this odd cough for a month or so; in September. My entire life I had never coughed outside of the beautiful winter months of the northeast.

Then this year I couldn’t breathe for nearly all of August, and my nose sort of itched. Eventually one of my clients goes, “Maybe you have allergies?”

I reply, “No, no, no. I have an immune system Zeus would envy.”

Client “Sometimes people develop them after being in a place for a few years.” (I’ve been in San Diego 3 years.)

Me “My eyes are a little itchy, but it’s mainly the coughing. I just don’t know why it won’t stop.”

Client “Uhh, you can cough from allergies.”

Me: “Wait, what? ARE YOU FUCKING SERIOUS?!?!”

After an intense bout of depression, at the behest of several people (I hate pills), eventually I went and took a Claritin. Of course things cleared up in the matter of an hour.

Side note: Buy the generic Claritin, lotradine, at Costco. You can literally buy 365 pills for like 8 dollars. Unlike my ignorant self who bought 10 pills for 10 dollars at 7-11. 

Next thing I know I’m popping antihistamines like the Jersey Shore used to pop collars. (What? Too soon? Screw you, I’m from Jersey; you’re not.)

I started thinking about the chronic affect of antihistamine use and how I really never researched this or have come across any discussion on it. Hence this article.

What is histamine / What do antihistamines do

For the purposes of this article, I’ll be referencing only H1 antihistamines. Basically all the ones you could buy at the grocery store. Benadryl, Claritin, Allegra, etc.

Some general information from Wikipedia, with words in plain english from me interspersed:

“Histamines produce increased vascular permeability, causing fluid to escape from capillaries into tissues”

Histamine helps fluids move between tissue, e.g. muscle.

“Histamine also promotes angiogenesis.”

Making of new blood vessels.

“Histamine triggers the inflammatory response.” 

And then antihistamines:

“Antihistamines suppress the histamine-induced wheal response (swelling) and flare response (vaosodilation) by blocking the binding of histamine to its receptors on nerves, vascular smooth muscle, glandular cells, endothelium, and mast cells. They exert a competitive antagonism to histamines.”

Prevent histamine from doing things like the aforementioned.

Now, in theory…

Logically, looking at the above one would assume taking antihistamines, that is, blocking the body’s inflammatory response, preventing the growth of new blood cells, decreasing the ability of fluids to transfer tissue, would have a negative impact on at least one thing -Exercise performance.

As I discussed in Post-workout…ibuprofen?, you want an inflammatory effect from exercise. This effect is what tells the body to adapt. Block the effect, block the adaptation. 


Two titles from what little research I could find on this topic:

Ingestion of an antihistamine does not affect exercise performance.

Acute antihistamine ingestion does not affect muscle strength and endurance

From the titles alone, you can interpret the findings. However, there is one study I found that appeared to find an impact:

Roles of histamine in exercised induced fatigue: Favoring endurance and preventing exercise against exhaustion

This study found that antihistamine use decreased walking endurance.There are some issues with this study though.

First, it was done on rats, not humans.

Second, as appears to be common with rat studies, they seemed to use insane doses. The study states they used things like Allegra at .1 ml per 10 grams of body weight.

So, if a rat weighed 100 grams: 100 grams / 10 = 10 instances of 10 grams of weight x .1 ml per 10 grams = 1 milliter of Allegra.

If someone like me weighs 90718 grams (200lbs): 90718 grams / 10 = 9071  x .1 = 907 millileters of Allegra. This is a tad more than the 30 ml max recommendation from Allegra.

This could very well explain why this study found acute effects on exercise performance while the human trials did not. In other words, it’s useless for our purposes.

What about chronic use?

An important factor to keep in mind is the above studies only dealt with antihistamine use in the acute. I can’t find anything on long-term use. As I stated though, logically, it makes sense chronic use of these pills would negatively affect things. It doesn’t appear many people are popping Allegra for 6 months straight though. Bringing us to…

Side-effects of antihistamines

From WebMD:

  • Dry mouth
  • Drowsiness
  • Dizziness
  • Nausea and vomiting
  • Restlessness or moodiness (in some children)
  • Trouble urinating or not being able to urinate
  • Blurred vision
  • Confusion

This is where I think things really come together. If you are someone who becomes worthless after a dosage of Benadryl, and you’re chronically taking it, then obviously being drowsy or knocked the hell out on a chronic basis is going to affect things.

As pertaining to this article, if you are chronically working out while drowsy, your workouts aren’t going to be as good, if your workouts aren’t as good then you are definitely risking negatively affecting your exercise ability and body composition.

One caveat

It’s worth mentioning that exercise can promote histamine production. So, if you’re someone with pretty severe symptoms (you’re already excessively producing histamine), and you exercise, there is a reasonable chance you could make your symptoms worse. Potentially to the point where you would want to avoid exercise.

However, take an antihistamine and this might allow you to exercise. So, it’s sort of: exercise in what is likely a less than ideal (drugged) state, or don’t exercise at all.

While you may be potentially preventing some of the benefits of exercise (if you’re drugging yourself chronically), I think it’s going to be hard for anyone to say just give up exercise. Less than ideal is better than nothing.

From what I can tell, few people are using allergy medication on a long-term basis anyways. It’s typically every now and then as they need it. In which case there appears to be very little concern.

My last (theoretical) recommendation would be this: Much like ibuprofen, I wouldn’t be surprised if there was something to the timing of the medication. For example, if you’re able to, take the antihistamine after working out. Ideally, you still get the benefits of the workout (because you didn’t block the adaptation) and then you receive your allergy med benefit as well. Hopefully by the time you work out again, say at least 24 hours later, the antihistamine has worn off.

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Posted in: Losing Weight