What Antihistamines Should be Used for Allergies?

Hi, I'm Dr. Dave Stukus. I'm a Professor of Clinical Pediatrics, a Board-Certified Allergist and Immunologist, and I'm also a member of the Medical and Scientific Council for the Asthma and Allergy Foundation of America.

What antihistamine should be used for allergies and what should be avoided?

We strongly recommend a thoughtful use of medications when treating symptoms of allergy and with antihistamines, these help block a chemical called histamine, and histamine is a is a major source of itching and sneezing, especially can also be a major source of hives and things like that. If your main symptoms are more nasal congestion, post nasal drip and runny nose, antihistamines aren't actually that helpful for that. So, we want to be thoughtful about the types of treatment that we use, and that's where we use things like nasal steroid sprays or nasal saline or sinus irrigation and things like that.

But if you do decide to use an antihistamine to help your symptoms, try to avoid the older first-generation antihistamines such as Benadryl or diphenhydramine. These are associated with tons of side effects and they don't last very long. And it takes a while for them to actually have an onset of action.

There are a widely available second-generation antihistamines and newer antihistamines that last longer. They don't sedation or major side effects, and they just work a lot better. So just being thoughtful about why we use antihistamines, what symptoms we’re treating and which ones we use. And for anybody out there who says that you have to switch any histamines every once in a while because your body becomes tolerant to it, I would say a couple of things. One. Well, maybe you're using antihistamines to treat the wrong symptoms. So again, they're not going to help congestion or post nasal drip or things like that, no matter how much you use. Or two, sometimes you know, the dose you're using, they may need to be adjusted a little bit.

So if you have concerns that the medicine that you're using isn't working for you, please discuss with your personal doctor or allergist.

What are the side effects of Benadryl?

Well, Benadryl has been around for over 80 years, and it was one of the first antihistamines that was ever developed and placed on the market. But that doesn't mean that we should still be using it. So, Benadryl is very nonselective, as are other first-generation antihistamines. So, it doesn't just bind to the histamine receptors that are causing your allergy symptoms. It can bind to other types of receptors throughout the body. This includes receptors in our heart, muscarinic receptors which are on our mucous membranes and can cause, you know, extreme dryness and things like that. It can cross into our brains and cause drowsiness and altered cognition. It can cause your heart rhythm to change and it can cause pretty serious side effects. It's been associated with early onset dementia for people who use first-generation antihistamines. So, it's very nonselective in the way that it works and we generally advise against using it.

There are misconceptions that Benadryl and first-generation antihistamines work faster than newer second-generation antihistamines. That's actually not the case. Second-generation antihistamines work faster. Lasts four times as long and don't have nearly the same side effects as the older first-generation antihistamines.

And lastly, if that doesn't convince you the FAA does not allow pilots to fly an airplane for 30 hours after taking a first-generation antihistamine. So that's a big deal. So, I strongly urge anybody who's operating a motor vehicle, if you have firearms, if you have to, you know, really rely on your senses for anything, please avoid first-generation antihistamines. Talk to your doctor about better alternatives.