Key takeaways:
Older antihistamines, such as diphenhydramine (Benadryl), can cause drowsiness. So it’s best to take them at night or when sleepiness isn’t a concern. But these antihistamines aren’t ideal for older adults due to risky side effects.
Newer antihistamines, such as loratadine (Claritin), are typically non-drowsy and have fewer side effects to consider. You can take them at any time of day and they work well for daily use to manage chronic allergies.
Oral antihistamines start working within a few hours, and you can take them with or without food. You can also combine antihistamines with other types of allergy medications — just avoid taking more than one antihistamine at the same time.
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Antihistamines are some of the most commonly used allergy medications. But they aren’t all created equal. Knowing the difference between daytime and nighttime versions of these allergy medications can help you choose the best option for your needs.
Read on to get pharmacist-backed tips for taking your antihistamine, including the best time to take them.
1. Know the difference between daytime and nighttime antihistamines
Knowing which oral antihistamines can make you drowsy and which don’t can help you know when to take them.
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The chart below summarizes daytime non-drowsy antihistamines versus nighttime drowsy antihistamines.
| Daytime / non-drowsy antihistamines | Nighttime / drowsy antihistamines |
|---|---|
|
|
*May cause drowsiness for some people
Older (first-generation) antihistamines, such as diphenhydramine, tend to cause drowsiness. This is because they cross the blood-brain barrier (BBB). The BBB filters what can reach your brain and spinal cord from your bloodstream. Antihistamines that cross the BBB are more likely to cause drowsiness.
If you’re home sick, daytime drowsiness may not be an issue for you. But if you’d prefer to stay awake and alert, it’s best to take these antihistamines at bedtime and avoid them during the day. These antihistamines are also a helpful choice to help you sleep if cold and allergy symptoms are keeping you awake. So they’re often included in “nighttime” cold and allergy medications.
Newer (second- and third-generation) antihistamines, such as loratadine, don’t cross the BBB as much. So they’re less likely to cause drowsiness. But they don’t keep you awake, either. And in most cases they only require once-daily doses. So it’s typically fine to take loratadine or other similar antihistamines at any time of day that works for your schedule.
Good to know: Histamine-2 receptor antagonists (H2 blockers) are another type of antihistamine medication. But they aren’t used for allergies. H2 blockers treat acid reflux and heartburn. They don’t typically cause drowsiness, but they may cause dizziness or fatigue for some people.
2. You can take antihistamines with or without food, but you should avoid alcohol
You can take antihistamines (all generations) with or without food. Stomach-related side effects aren’t common. And food doesn’t affect how these medications work. So you can typically take them at any time that’s convenient for you, regardless of mealtimes.
But it’s best to avoid combining alcohol with antihistamines — especially ones that can make you drowsy. This combination could lead to excessive sedation and impaired thinking.
3. You can combine antihistamines with other allergy medications
It’s safe to combine antihistamines with other types of allergy medications. Examples include steroid nasal sprays, such as fluticasone (Flonase) or a decongestant, such as pseudoephedrine (Sudafed). These medications work differently and don’t interact with each other. But you shouldn’t take more than one antihistamine at the same time.
You can often find antihistamines and pseudoephedrine in a combination pill, such as Claritin-D (loratadine / pseudoephedrine). These products are typically kept behind the pharmacy counter.
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4. Taking an antihistamine daily works best for chronic allergy symptoms
Antihistamines typically start working within a few hours. So they’re a helpful option for fast allergy symptom relief when you need it.
But antihistamines work best for chronic allergies when you take them on a daily basis. Second-generation antihistamines are typically the best choice for daily use. This is because they have fewer side effects and more convenient once-daily doses compared with older antihistamines.
5. Know what side effects to expect from your antihistamine
Drowsiness isn’t the only side effect that’s different between first- and second/third-generation antihistamines. Knowing the common side effects of each type can help you choose the treatment that works best for your needs.
Common side effects of diphenhydramine and other first-generation antihistamines include:
Drowsiness
Dizziness
Headache
Constipation
Blurry vision
Trouble peeing
Ringing in the ear (tinnitus)
Confusion (especially in older adults)
These antihistamines typically aren’t recommended for older adults, since they can raise the risk of confusion and falls. It’s also best to review your medication list with a healthcare professional before taking them, since they can interact with other medications.
Newer antihistamines are much less likely to cause these side effects. They also have fewer interactions to consider. So they’re a safer option for older adults. But cetirizine and levocetirizine may cause drowsiness for some people. And both of these medications can also cause severe itching when you stop taking them, especially after long-term use (several months or more).
Good to know: Older antihistamines have a drying effect on the body. This can lead to side effects such as dry mouth and constipation. But it’s also what makes them effective for cold and flu symptoms that aren’t related to allergies. Newer allergy medications won’t help dry up a runny nose that’s caused by anything other than allergies.
How to save on the cost of your antihistamine
Most antihistamines are available OTC and are relatively affordable. But you can still save on their cost with a free GoodRx discount. You’ll just need a prescription first.
Taking the generic version of an antihistamine can lower costs, too. Generic medications are a great way to save money without sacrificing quality. So keep that in mind when you’re making your selection.
Below, we’ve provided a table for you to easily compare costs of popular brand-name and generic antihistamines.
Medication name | Average cash price | Lowest GoodRx price |
|---|---|---|
Allegra (30 tablets, 180 mg) | ||
Fexofenadine (30 tablets, 180 mg) | ||
Benadryl (30 tablets, 25 mg) | ||
Diphenhydramine (30 tablets, 25 mg) | ||
Claritin (30 tablets, 10 mg) | ||
Loratadine (30 tablets, 10 mg) | ||
Zyrtec (30 tablets, 10 mg) | ||
Cetirizine (30 tablets,10 mg) | ||
Clarinex (30 tablets, 5 mg)* | ||
Desloratadine (30 tablets, 5 mg)* | ||
Hydroxyzine hydrochloride (30 tablets, 25 mg)* |
* Prescription only
The bottom line
Antihistamines are common allergy medicines, but they don’t all have the same effects. Older antihistamines, such as diphenhydramine (Benadryl), can make you drowsy. So it’s better to take them at night or when you don’t mind feeling sleepy. But they aren’t the best choice for older adults.
Newer antihistamines, such as loratadine (Claritin), don’t typically cause drowsiness. So you can take them at any time of day. And they’re typically safer and cause fewer side effects than older antihistamines. Newer antihistamines are also the best choice to take daily for chronic allergy symptoms.
Antihistamines start working within a few hours of taking them. You can take antihistamines with or without food. It’s also fine to combine them with other types of allergy medications, such as a steroid nasal spray or decongestant. But you shouldn’t take more than one antihistamine at the same time.
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References
Daneman, R., et al. (2015). The blood-brain barrier. Cold Spring Harbor Perspectives in Biology.
Farzam, K., et al. (2021). Antihistamines. StatPearls.
Seidman, M. D., et al. (2015). Clinical practice guideline: Allergic rhinitis. Otolaryngology–Head and Neck Surgery.
Simon, F. E. R., et al. (2008). H1 antihistamines: Current status and future directions. World Allergy Organization Journal.
