5 Pharmacist-Backed Tips for Taking Antihistamines

Antihistamines are some of the most commonly used medications. Most people think of them as being for seasonal allergies. But this applies to only some of the available antihistamines. In fact, certain antihistamines can play a role in treating heartburn or even stomach ulcers.

Many antihistamines are available over-the-counter (OTC). But some are still prescription-only medications. Antihistamines come in many different forms, ranging from capsules and tablets to liquids and injections. As helpful as they can be, these medications can cause some bothersome side effects. 

So in this article, we’ll discuss some helpful tips for taking your antihistamine, including the best time to take them. 

What are the different antihistamines available?

There are two major classes of antihistamines available: histamine-1 (H1) receptor blockers and histamine-2 (H2) receptor blockers. H1 blockers are commonly used for allergies and allergic reactions. H2 blockers are used to treat stomach-related problems caused by too much stomach acid.

H1 blockers can be broken down even further into first- and second-generation H1 antihistamines. First-generation H1 antihistamines are older and tend to cause more brain and nervous system side effects, like drowsiness. Second-generation H1 antihistamines started coming to the U.S. market in the 1980s. As we’ll detail below, they’re less likely to make you sleepy or cause other side effects.

Examples of first-generation H1 antihistamines:

• Chlorpheniramine

• Diphenhydramine (Benadryl)

• Doxylamine (Unisom)

• Hydroxyzine (Atarax, Vistaril)

Examples of second-generation H1 antihistamines:

• Cetirizine (Zyrtec)

• Desloratadine (Clarinex)

• Fexofenadine (Allegra)

• Levocetirizine (Xyzal)

• Loratadine (Claritin)

Examples of H2 blockers:

• Cimetidine (Tagamet HB)

• Famotidine (Pepcid, Zantac 360)

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5 tips for taking antihistamines

Whenever people start a new medication, they often wonder about the best way to take it. So here, we’ll discuss some helpful tips, starting with the best time to take antihistamines.

1. When is the best time to take antihistamines?

Depending on the type of antihistamine you’re taking, it may be best to take it at bedtime.

First-generation H1 antihistamines tend to cause drowsiness. This is because they can cross something called the blood-brain barrier (BBB). The BBB is a set of blood vessels designed to protect the brain and spinal cord from being exposed to outside threats. If a medication crosses the BBB, it may cause brain or nervous system side effects, like drowsiness.

Second-generation H1 antihistamines don’t cross the BBB as much. As such, they’re less likely to cause drowsiness. H2 blockers don’t easily cross the BBB either. So drowsiness isn’t a typical side effect of theirs either.

To sum it up, all first-generation H1 antihistamines should be taken close to bedtime or when you’re able to sleep. Second-generation H1 antihistamines and H2 blockers can typically be taken at any time of the day. One exception to this is cetirizine, which can cause drowsiness for up to 14% of those who take it.

2. Should I take my antihistamines with food?

H1 antihistamines (both generations) can be taken with or without food. Stomach-related side effects aren’t common with these antihistamines. Food doesn’t affect how these medications work.

H2 blockers are best taken about 30 to 90 minutes before eating a meal. If you’re taking an H2 blocker once a day, you should take it before the same meal every day. This will provide the most consistent results. If you’re taking an H2 blocker twice a day, you should take it before your morning and evening meals.

3. Should I separate my antihistamines from other allergy medications?

You don’t have to. It’s safe to combine antihistamines with other allergy medications, like fluticasone propionate (Flonase) or pseudoephedrine (Sudafed). These medications work differently and don’t interact with each other. The thing you want to avoid is taking two antihistamines together. This can raise your risk of side effects.

However, there are times where taking both an H1 antihistamine and an H2 blocker might be necessary. For example, this combination has been used for chronic hives for several decades. But you should only take them together after talking to a healthcare provider.

4. What happens if I miss my dose of my antihistamine?

If you miss a dose of your antihistamine, you may feel a return of your symptoms. First-generation H1 antihistamines only last for about 4 to 6 hours before wearing off. Second-generation H1 antihistamines can last for 12 to 24 hours. H2 blockers can also continue working for up to 24 hours.

Generally speaking, if you miss a dose, you should take it as soon as you remember. But if you take an antihistamine daily and it’s close to your next dose, you should skip it. Take your next scheduled dose at its usual time. Never double up on or take extra of your antihistamine. If you’re not sure whether you should take a missed dose or not, contact your pharmacist.

5. What can I do if I experience side effects from my antihistamine?

Some possible side effects of H1 antihistamines include:

• Drowsiness

• Dry mouth

• Dizziness

• Trouble focusing

• Ringing in the ear (tinnitus)

These side effects tend to be more common with first-generation H1 antihistamines. But they can happen with second-generation H1 antihistamines, too. If side effects are excessive or affect your daily routine, stop the medication and speak with your healthcare provider. There may be other options that they can recommend.

Side effects with H2 blockers aren’t common. Headaches, diarrhea, and dizziness can happen for some people. But you should talk to a healthcare provider if you experience any side effects while taking H2 blockers.

Tips on how to save money on your antihistamine

Most antihistamines are available OTC and are inexpensive. But even if they’re OTC, you can still use a GoodRx coupon to help save you money. You’ll just need to ask a healthcare provider to write a prescription for it. Then, let the pharmacy know you’d like to use a GoodRx coupon for it.

Taking generic versions of a medication 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.

Prices current as of June 9, 2022.

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Written by:

Sonia Amin Thomas, PharmD, BCOP

Sonia Amin Thomas, PharmD, BCOP, has been practicing as a clinical pharmacist for 12 years and in oncology pharmacy for over 10 years. She practices both academic and clinical pharmacy and is board certified as an oncology pharmacist and integrative health coach.

Edited by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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