7 Tips for Choosing the Right OTC Antihistamine
Key takeaways:
Over-the-counter (OTC) antihistamines are commonly used to treat allergies. Some can also treat nausea and help you sleep.
There are different categories (or generations) of OTC antihistamines. First-generation antihistamines include diphenhydramine (Benadryl). Second- and third-generation antihistamines include loratadine (Claritin) and fexofenadine (Allegra).
Second- and third-generation antihistamines are preferred for allergies, especially in older adults. They work quickly and are usually only taken once a day. And they generally have fewer side effects than first-generation antihistamines.
Table of contents
Over-the-counter (OTC) antihistamines are convenient options to treat allergy symptoms, like congestion, runny nose, and itching. Some OTC antihistamines can also help with nausea and trouble sleeping (insomnia).
Zyrtec, Allegra, and Benadryl are some of the most popular brand-name antihistamines. But did you know there are different types of antihistamines that have different effects on your body?
Below, we’ll discuss seven tips to help you choose the best OTC antihistamine for you.
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1. Know the two categories of OTC antihistamines
“Antihistamine” is a broad term. It refers to two groups of medications that treat completely different health conditions:
Histamine-1 (H1) receptor blockers are commonly used for allergies, allergic reactions, and to help with sleep.
Histamine-2 (H2) receptor blockers treat conditions caused by too much stomach acid, like heartburn and gastroesophageal reflux disease (GERD).
In this article, we’ll focus on H1 blockers. H1 blockers are divided into two categories:
First-generation antihistamines
Second- and third-generation antihistamines
First-generation antihistamines
First-generation antihistamines are the “older” antihistamines. They’ve been around longer than second- and third-generation antihistamines, which we’ll discuss next. Examples of OTC first-generation antihistamines include:
Diphenhydramine (Benadryl, ZzzQuil)
Dimenhydrinate (Dramamine)
Chlorpheniramine (ChlorTabs)
Doxylamine (Unisom SleepTabs)
These medications are well-known for causing sleepiness. And in some cases, this is the exact reason they’re used. But some first-generation antihistamines can be used for other reasons too. This includes allergies, allergic reactions, and nausea.
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Second- and third-generation antihistamines
Second- and third-generation antihistamines are the “newer” antihistamines. Examples of OTC second-generation antihistamines include:
Loratadine (Claritin)
Cetirizine (Zyrtec)
Levocetirizine (Xyzal Allergy)
Fexofenadine (Allegra) is the only third-generation antihistamine.
Second- and third-generation antihistamines cause less drowsiness than first-generation antihistamines. They’re used to treat allergies.
2. OTC antihistamines are available under many different names
OTC antihistamines are found in many “combination” products for allergies, sleep, and cold or flu. These are products that contain two or more ingredients in a single medication. Some examples include:
Advil PM (ibuprofen/diphenhydramine)
Tylenol PM Extra Strength (acetaminophen/diphenhydramine)
Claritin-D (loratadine/pseudoephedrine)
Allegra-D (fexofenadine/pseudoephedrine)
Zyrtec-D (cetirizine/pseudoephedrine)
If you take any OTC products, make sure you read the labels carefully so you know exactly what’s in them. If you aren’t sure what’s in the products you take, talk to your pharmacist. They can help make sure you’re not doubling up on antihistamines accidentally. Taking too many oral antihistamines can lead to a greater chance of side effects or even an antihistamine overdose. Symptoms may include a fast or racing heartbeat, behavioral changes, or poor balance. More seriously, it can lead to cardiac arrest and seizures.
3. Not all OTC antihistamines work the same way
Antihistamines work by blocking the effects of histamine. Histamine is a natural chemical in your body that’s released in many situations. One of these situations is when you experience inflammation, like with allergies. Histamine release can cause symptoms like itching, sneezing, and congestion.
But first-generation antihistamines are different from second- and third-generation antihistamines. First-generation antihistamines are able to pass into the brain. This is why they cause drowsiness. But second- and third-generation antihistamines don’t cross into the brain as much. So they don’t cause as much drowsiness.
4. There are differences in how you take different OTC antihistamines
There are some key differences between the different groups of OTC antihistamines. This includes how you take them. We’ll summarize some of these major differences below:
First-generation | Second- and third-generation | |
How long they last | Generally 4-6 hours | 12-24 hours |
Dosing | May need to be taken up to 4-6 times daily (if used for allergies) | Taken 1-2 times daily for allergies |
Best time to take them | If only taking once a day, best to take close to bedtime due to drowsiness | Anytime of day |
Some people take antihistamines as needed for allergy symptoms. But others may struggle to control allergy symptoms on a daily basis. In this case, daily use of second- or third-generation antihistamines may be recommended.
If you have seasonal allergies, starting an oral antihistamine at least 2 weeks before allergy season may be helpful.
5. Some OTC antihistamines work faster than others for allergies
Some OTC antihistamines start working faster than others for treating allergies. In general, second- and third-generation antihistamines work more quickly than first-generation antihistamines. And as discussed above, their effects last longer, too.
Starts working within | |
Benadryl | 2 hours |
Chlorpheniramine | 3 hours |
Claritin | 2 hours |
Allegra | 2 hours |
Xyzal Allergy | 1 hour |
Zyrtec | 1 hour |
6. OTC antihistamines have possible side effects (especially first-generation antihistamines)
Possible side effects of first-generation antihistamines include:
Drowsiness
Dry mouth and eyes
Trouble peeing
Constipation
Dizziness
Ringing in the ear (tinnitus)
Trouble with focus, memory
Impaired balance that can increase risk of falls
These side effects are possible with second- and third-generation antihistamines, but much less likely. Of the second-generation antihistamines, cetirizine is most likely to cause drowsiness. This is especially true at doses higher than what’s usually prescribed (greater than 10 mg).
7. It’s best to avoid certain OTC antihistamines if you’re over 65
The American Geriatrics Society (AGS) has created a list of medications that are risky for older adults. This list, called the AGS Beers List, identifies medications that should be used with caution (and ideally avoided) in people who are over 65.
All first-generation antihistamines, including Benadryl, are on this list. So if you’re over 65, it’s best to avoid these medications. Taking them can put you at increased risk of falls, confusion, and even changes in mental status.
The bottom line
OTC antihistamines are commonly used to treat allergies. They can be divided into two categories: first-generation antihistamines and second- and third-generation antihistamines. A common first-generation antihistamine is Benadryl. Second- and third-generation antihistamines include Claritin and Allegra.
Second- and third-generation antihistamines are preferred to first-generation antihistamines for allergies. This is especially true in older adults. First-generation antihistamines cause more side effects (like drowsiness) and may need to be taken multiple times a day. Second- and third-generation antihistamines work relatively quickly and usually only have to be taken once a day.
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References
2019 American Geriatrics Society Beers Criteria Update Expert Panel. (2019). American Geriatrics Society 2019 updated AGS Beers criteria for potentially inappropriate medication use in older adults. Journal of the American Geriatrics Society.
American College of Allergy, Asthma & Immunology. (2017). Seasonal allergies.
Farzam, K., et al. (2022). Antihistamines. StatPearls.
Simons, F. E. R., et al. (2008). H1 antihistamines: Current status and future directions. World Allergy Organization Journal.
Thangam, E. B., et al. (2018). The role of histamine and histamine receptors in mast cell-mediated allergy and inflammation: The hunt for new therapeutic targets. Frontiers in Immunology.
