Pronunciation: uh-l-EH-g-r-uh
Generic name: fexofenadine
Dosage form: tablets, oral suspension
Drug class: Antihistamines

Medically reviewed by Melisa Puckey, BPharm. Last updated on Oct 28, 2025.

What is Allegra?

Allegra (fexofenadine) is an antihistamine used to treat allergy symptoms, including sneezing, itching, watery eyes, and a runny nose in adults and children. Allegra can also be used to treat hives caused by a condition called chronic idiopathic urticaria in adults and children over 12 years of age.  Allegra-D is used for nasal and sinus congestion caused by allergies and colds; it contains fexofenadine and pseudoephedrine.

Allegra is available over the counter without a prescription.

Allegra works by selectively blocking histamine-1 receptors. Histamine is a chemical released by mast cells in response to an allergen, and it is responsible for many allergy symptoms, such as watery eyes, a runny nose, sneezing, itching, and hives. By binding to histamine receptors, Allegra prevents histamine from having an effect on these receptors, which reduces allergy symptoms.

Allegra is a second-generation antihistamine that is much less likely to cause drowsiness and sedation compared with some older antihistamines. This is because it does not does not easily cross the blood-brain barrier.

Fexofenadine was FDA-approved in 1996.

Warnings

All Allegra medications 

Do not use this medicine if you've ever had an allergic reaction to it or any of its ingredients.

Do not take Allegra with fruit juice (such as apple, orange, or grapefruit).

Warnings for Allegra Hives

Get emergency help immediately if you have hives along with any of the following symptoms:
Trouble swallowing, dizziness or loss of consciousness, swelling of tongue, swelling in or around mouth, trouble speaking, wheezing or problems breathing or drooling.

These symptoms may be signs of anaphylactic shock. This condition can be life-threatening if not treated by a health professional immediately. Symptoms of anaphylactic shock may occur when hives first appear or up to a few hours later.

Not a Substitute for Epinephrine.
If your doctor has prescribed an epinephrine injector for "anaphylaxis" or severe allergy symptoms that could occur with your hives, never use this product as a substitute for the epinephrine injector. If you have been prescribed an epinephrine injector, you should carry it with you at all times.

Do not use this product to prevent hives from any known cause, including: foods, insect stings, medicines, latex or rubber gloves. In these instances, this product will not stop hives from occurring.

Avoiding the cause of your hives is the only way to prevent them.
Hives can sometimes be serious. If you do not know the cause of your hives, see your doctor for a medical exam. Your doctor may be able to help you find a cause.

Ask a doctor before use if:.

• Your hives that are an unusual color, look bruised or blistered.
• You have hives that do not itch.

Stop using this medicine and ask a doctor if you have:

• An allergic reaction to this product occurs. Seek medical help right away.
• Symptoms do not improve after 3 days of treatment.
• The hives have lasted more than 6 weeks.

Warning for Allegra-D tablets

Do not take Allegra-D 24 HR if you: 

• Are currently taking a prescription monoamine oxidase inhibitor (MAOI) for depression, psychiatric, or emotional conditions, or Parkinson’s disease.
• Do not use Allegra-D 24 HR for 2 weeks after stopping the MAOI drug. If you are unsure if your prescription medicine is an MAOI, ask your doctor or pharmacist before taking this product.
• You have difficulty swallowing.

Before taking this medicine

You should not use Allegra if you are allergic to it or any of the inactive ingredients.

Ask a doctor or pharmacist if this medicine is safe to use if you have:

• kidney disease.

Ask a doctor before using Allegra if you are pregnant or breastfeeding.

Older adults may be more sensitive to the effects of this medicine. If you are 65 or older, ask a doctor before taking this medicine.

This medicine may contain phenylalanine and could be harmful if you have phenylketonuria (PKU).

While using this product:

• Only take the recommended amount
• Don't take it with aluminum or magnesium antacids
• Avoid fruit juices.
• Stop using it and see a doctor immediately if you have an allergic reaction. Get medical help right away.

How should I take Allegra?

Take Allegra exactly as directed on the label, or as prescribed by your doctor.

Take this medicine only with water.

Take the disintegrating tablet on an empty stomach.

Shake the oral suspension (liquid) before you measure a dose. Use the dosing cup provided, or use a medicine dose-measuring device (not a kitchen spoon).

Children's Allegra Allergy 12-hour Dissolve Tabs should only be removed from the package just before they are taken. Place the tablet on the tongue and allow it to dissolve, without chewing. Swallow several times as the tablet dissolves.

Allegra-D Allergy & Congestion tablets should be swallowed whole. Do not divide, crush, chew, or dissolve the tablet.

Call your doctor if your symptoms do not improve or if they get worse.

Store this medicine in its original package at room temperature, away from moisture and heat. Do not allow liquid medicine to freeze.

Allegra dosing information

Allegra Allergy 24-hour Tablets

Use: allergy symptoms, including sneezing, runny nose, itchy or watery eyes, itchy nose or throat.

Dose: 

• Adults and Children 12 years and over: Take one 180 mg tablet with water once a day; do not take more than 1 tablet in 24 hours.
• Children under 12 years of age: Do not use.

Allegra Allergy 12 Hour Tablets

Use: allergy symptoms, including sneezing, runny nose, itchy or watery eyes, itchy nose or throat.

Dose:

• Adults and children 12 years of age and over: Take one 60 mg tablet with water once every 12 hours; do not take more than 2 tablets in 24 hours.
• Children under 12 years of age: Do not use.

Children's Allegra Allergy 12-hour Dissolve Tabs

Use: allergy symptoms, including sneezing, runny nose, itchy or watery eyes, itchy nose or throat

Dose:

• Adults and Children 12 years and over: Take two 30mg tablets every 12 hours on an empty stomach; do not take more than 4 tablets in 24 hours.
• Children 6 years to under 12 years old: Take one 30mg tablet every 12 hours on an empty stomach; do not take more than 2 tablets in 24 hours​.
• Children under 6 years: Do not use
• Instructions: Place 1 tablet on the tongue; tablet disintegrates, with or without water

Children's Allegra Allergy 12 Hour Liquid (30mg/5mL)

Use: allergy symptoms, including sneezing, runny nose, itchy or watery eyes, itchy nose or throat

Dose:

• Adults and Children 12 years and over: Take 10 mL every 12 hours. Do not exceed 20 mL in 24 hours.
• Children 2 years to under 12 years: Take 5 mL every 12 hours. Do not exceed 10 mL in 24 hours.
• Children under 2 years old and adults 65 years and older: Check with a doctor first.

Allegra Hives 24-hour Tablet

Use: To reduce hives and itching due to hives (urticaria)

Dose: 

• Adults and children 12 years of age and over: Take one 180 mg tablet with water once a day; do not take more than 1 tablet in 24 hours.
• Children under 12 years of age: Do not use.

Allegra-D Allergy & Congestion 24 HR

Use: To relieve nasal and sinus congestion due to colds or allergies. Also to relieve sneezing, runny nose, itchy or watery eyes, itchy nose or throat.

Dose:

• Adults and children 12 years of age and over: Take one tablet with water once a day on an empty stomach; do not take more than 1 tablet in 24 hours.
• Children under 12 years of age: Do not use.
• Do not divide, crush, chew or dissolve the tablet; swallow the tablet whole.

Allegra-D Allergy & Congestion 12 HR

Use: To relieve nasal and sinus congestion due to colds or allergies. Also to relieve sneezing, runny nose, itchy or watery eyes, itchy nose or throat.

Dose:

• Adults and children 12 years of age and over: Take one tablet with water once every 12 hours on an empty stomach; do not take more than 2 tablets in 24 hours.
• Children under 12 years of age: Do not use.
• Do not divide, crush, chew or dissolve the tablet; swallow the tablet whole.

General dosing information for all products

Ask a doctor before using Allerga if your child or you have any kidney issues or are over 65 years old.

What happens if I miss a dose?

Allegra is used when needed. If you are on a dosing schedule, skip any missed dose. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms of this medicine may include a dry mouth, dizziness, or drowsiness.

What should I avoid while taking this medicine?

Do not take this medicine with fruit juice (such as apple, orange, or grapefruit). These juices can make it harder for your body to absorb the active ingredient fexofenadine.

Do not take with antacids containing aluminum or magnesium.

Ask a doctor or pharmacist before using other cough or cold medicines that may contain similar ingredients.

Allegra side effects

Get emergency medical help if you have signs of an allergic reaction to fexofenadine: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Fexofenadine may cause serious side effects. Stop using fexofenadine and call your doctor at once if you have:

• flu-like symptoms (fever, chills, unusual tiredness);
• new or worsening cough;
• pain; or
• signs of an ear infection--fever, ear pain or full feeling, trouble hearing, drainage from the ear, fussiness in a child.

Common side effects of fexofenadine may include:

• headache;
• back pain; or
• cold symptoms such as stuffy nose, sinus pain, sore throat.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Related/similar drugs

What other drugs will affect Allegra?

Using Allegra with other drugs that make you drowsy can worsen this effect. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Do not take with antacids containing aluminum or magnesium.

Ask a doctor or pharmacist before using fexofenadine with any other medications, especially:

• ketoconazole; or
• erythromycin.

This list is not complete. Other drugs may affect fexofenadine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.

Company 

Chattem, Inc., a Sanofi Company, Chattanooga, TN

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