What Can You Not Take with Allegra? 9 Common Questions About Allegra Interactions

Allegra (fexofenadine) is an over-the-counter (OTC) antihistamine. It treats common allergy symptoms, such as sneezing and runny nose. It’s a top choice for many people since it’s non-drowsy and doesn’t typically cause many side effects.

But is it safe to take with your other medications? Luckily, Allegra doesn’t have many interactions. But there are still a few that you should know about. Here’s what you can and can’t take with Allegra.

1. What can you not take with Allegra?

Many people are surprised to learn that the most common Allegra interactions are caused by things you may already have in your fridge or medicine cabinet. Here are three combinations to avoid.

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Fruit juice

You shouldn’t take Allegra around the same time as fruit juice. This includes grapefruit, orange, and apple juices. These beverages decrease how much Allegra gets absorbed from the digestive tract into your body. And this could make the medication less effective. To avoid this interaction, you’ll need to separate Allegra from fruit juice by at least 4 hours. 

Green tea

Similar to fruit juice, green tea can block Allegra from being absorbed. So it may be less effective when taken with green tea.

Keep in mind that some green tea extracts and dietary supplements are very concentrated or may release slowly over several hours. You may need to avoid combining these products with Allegra completely.

Antacids

You also shouldn’t take Allegra with antacids that contain magnesium or aluminum. These antacids decrease the amount of Allegra that gets absorbed into your body. This could make Allegra less effective.

Many OTC antacids contain magnesium or aluminum, including:

• Milk of Magnesia (magnesium hydroxide)

• Rolaids (calcium carbonate / magnesium hydroxide)

• Mylanta (aluminum hydroxide / magnesium hydroxide / simethicone)

It’s best to separate these antacids from Allegra by a few hours. You could also try a heartburn medication that doesn't contain magnesium or aluminum, such as Tums (calcium carbonate).

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2. Which prescription medications interact with Allegra?

Luckily, Allegra doesn't interact with many prescription medications. But there are a few notable ones to watch out for.

Erleada

Erleada (apalutamide) is a prostate cancer medication. It may prevent your body from fully absorbing Allegra, possibly lowering its effectiveness. If you’re taking Erleada, talk to your cancer care team about alternative allergy medications.

Oral ketoconazole

Oral ketoconazole is an antifungal medication that may be prescribed for severe fungal infections. It’s usually not a first-choice medication because it interacts with many other medications, including Allegra, and has other risks.

When taken together, ketoconazole can increase levels of Allegra in your body. This can raise the risk of side effects from Allegra, such as headaches. If you’re taking oral ketoconazole, talk to your prescriber or pharmacist about allergy treatments that are safer to combine with it.

Oral erythromycin 

Erythromycin (Ery-Tab) is an antibiotic. When taken orally, it can interact with Allegra. Similar to ketoconazole, erythromycin increases the amount of Allegra that gets absorbed into your body. This can lead to more Allegra side effects.

It’s a good idea to avoid combining Allegra and erythromycin. Speak to your healthcare team about allergy medications that are safe to take with this antibiotic.

3. Can you take Allegra and Sudafed together?

Yes. For most people, it’s safe to combine Allegra with Sudafed (pseudoephedrine). Sudafed can be a helpful, short-term addition for treating nasal congestion. In fact, you can find both medications already combined in one pill called Allegra-D (fexofenadine / pseudoephedrine).

But Sudafed isn’t right for everyone. It can cause side effects including increased heart rate and blood pressure. These side effects can be dangerous for people with certain health conditions, such as heart disease.

Good to know: The dose of pseudoephedrine in Allegra-D is higher than what’s included in many Sudafed tablets. When taking Allegra and Sudafed together, consider taking them as separate pills if you want to limit the side effects of pseudoephedrine.

4. Does Allegra interact with blood pressure medication?

Allegra doesn’t have any listed interactions with blood pressure medications. And antihistamines such as Allegra aren’t known to elevate blood pressure, either. But as mentioned above, Allegra is sometimes combined with pseudoephedrine (the Allegra-D line). This could worsen symptoms of the condition you’re taking blood pressure medications to treat.

If you have a heart condition or high blood pressure, it’s best to stick with just plain Allegra. Decongestants, including the one in Allegra-D, can cause blood pressure and heart rate changes.

5. Can you take Allegra with cold medicines such as NyQuil?

Maybe. But you need to be cautious when doing so. Nyquil (acetaminophen / dextromethorphan / doxylamine) and many other combination cold medicines already have an antihistamine in them. Taking more than one oral antihistamine doesn’t provide additional symptom relief. But it can cause side effects, some of which could be serious.

When picking a cold medication, carefully read the OTC label. Look for the list of active ingredients and what each one does. If you see an antihistamine listed, avoid taking that cold medication with Allegra. If you’re unsure what to pick, your pharmacist can help you select a product that’s safe to take.

6. Can you take Allegra and Flonase together?

Yes. You can safely combine Allegra with Flonase (fluticasone propionate) or other steroid nasal sprays. This can be helpful when you first start treating allergies. Allegra starts working within 2 hours, while Flonase can take up to 2 weeks to kick in.

Taking these medications together can help bridge the gap until Flonase is fully working. But experts suggest that taking the combination long term likely doesn’t provide much extra benefit compared with using Flonase by itself.

7. Can you take Allegra and Tylenol together?

Yes. Most people can safely combine Allegra with Tylenol (acetaminophen). Allergy symptoms often come with a sinus headache, which acetaminophen can help relieve.

But keep in mind that acetaminophen may not be the best pain reliever for everyone. If you have liver problems or drink alcohol regularly, talk to a healthcare professional before taking acetaminophen. While taking Allegra is still safe under these circumstances, adding acetaminophen to these situations can raise your risk of liver damage.

8. Can you take Allegra and Advil together?

Yes. It’s fine for most people to take Allegra with Advil (ibuprofen) or another nonsteroidal anti-inflammatory drug (NSAID). Advil can be a helpful option for relieving pain and swelling from a sinus headache.

But some people with kidney problems may need to avoid this combination. If you have kidney disease, talk to a healthcare professional before taking Allegra or NSAIDs. You may need to take a lower dose of Allegra. And NSAIDs, such as Advil, can sometimes cause or worsen kidney problems.

9. Can you take Allegra and amoxicillin together?

Yes. It’s generally safe to combine Allegra with amoxicillin (Amoxil) or most other antibiotics. As discussed above, erythromycin is an exception to this.

But if you’re taking amoxicillin or another antibiotic to treat a sinus infection, ask a healthcare professional before adding Allegra. Antihistamines, such as Allegra, can actually worsen sinus infection symptoms in some cases.

How can I find out more about Allegra interactions?

Always tell your prescriber and pharmacist about all your health conditions and medications, including herbal supplements. They can screen for drug interactions between Allegra and other medications or supplements. Don’t be surprised if they also ask you about the food and drinks you consume. Remember that some of Allegra’s most common interactions are with fruit juice and green tea.

Pharmacist tip: To better screen for interactions, it’s helpful to keep an updated medication list to share with everyone on your healthcare team.

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Written by:

Tegan Smedley, PharmD, APh

Tegan Smedley, PharmD, APh, has 10 years of experience as a pharmacist. She has worked in a variety of settings, including retail, hospital, and ambulatory care.

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:

Austin Ulrich, PharmD, BCACP

Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. In his early career, he provided direct patient care in a variety of settings, including hospital and community pharmacies, and in a primary care clinic as a clinical pharmacist.

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