Understanding Allegra-D's Active Ingredients: The Science Behind Allergy and Congestion Relief

Discover the dual-action formula of Allegra-D that offers comprehensive relief from seasonal allergies and congestion.

A woman comparing Allegra® with another medicine in the allergy aisle at a store, looking approvingly towards Allegra®.

The signs and symptoms of allergies, common colds, and other illnesses can have many similarities—making it difficult to figure out how to best relieve your symptoms. But there are a few ways to identify which is which and continue living your greatness, by understanding the most common allergy symptoms to look out for.1

In this article, you will find information about

What are the active ingredients in Allegra-D?

When it comes to finding relief from seasonal allergies with congestion, Allegra-D stands out as a go-to medication for many. At the core of its effectiveness are two primary active ingredients: Fexofenadine Hydrochloride and Pseudoephedrine Hydrochloride. Together, these compounds form a powerful duo that targets a range of symptoms, offering a comprehensive solution for those struggling with allergic reactions and nasal congestion.

Fexofenadine Hydrochloride: The Antihistamine Powerhouse

Fexofenadine Hydrochloride, commonly known as Fexofenadine, is a second-generation antihistamine. Unlike its first-generation counterparts, which often cause drowsiness, Fexofenadine is designed to minimize such side effects. It is effective in alleviating allergy symptoms like sneezing, runny nose, and itchy or watery eyes.

Pseudoephedrine Hydrochloride: The Decongestant Dynamo

The "D" in Allegra-D stands for Decongestant and Pseudoephedrine is the specific decongestant in Allegra-D. Pseudoephedrine is the most potent oral decongestant ingredient that is available over-thecounter (OTC) at the pharmacy. This powerful compound acts as a beacon of relief for individuals plagued by the discomfort of nasal and sinus congestion. Tracing its roots to the Ephedra family, pseudoephedrine boasts a storied medicinal history, spanning over 5,000 years in China and 2,000 years in the Middle East1 . Its efficacy lies in its ability to constrict the blood vessels within the nasal passages, thereby diminishing swelling and facilitating easier breathing. In simple terms, just one dose of pseudoephedrine could make a big difference in relieving nasal congestion, making it more effective than another common oral decongestant, phenylephrine (PE) 7.

What is the Science Behind Allegra-D?

We've all been there—sniffling, sneezing, and feeling congested when seasonal allergies hit. It's not just uncomfortable; it's downright frustrating. So, how does Allegra-D offer that much-needed relief when other medications fall short? Let's delve into the science behind its active ingredients to find out.

The Role of Histamines in Allergies

When an allergen invades your system, your body's natural defense mechanism kicks in, releasing a substance called histamine. While histamine serves a protective role, it's also the culprit behind those pesky allergy symptoms like itchy eyes and a runny nose.

Fexofenadine: Blocking Histamines

Fexofenadine comes into play here as a non-drowsy antihistamine. It blocks the effects of histamine, effectively reducing allergy

Pseudoephedrine: Tackling Nasal Congestion

If you've ever felt like your face was being squeezed by an invisible hand, you're not alone. That sensation is sinus pressure, and it's as uncomfortable as it sounds. Pseudoephedrine, the "D" in Allegra-D, targets this discomfort by narrowing the blood vessels in your nasal passages. The result? Easier breathing and less facial discomfort3.

The Combined Effectiveness of Fexofenadine and Pseudoephedrine

When used in combination, these two active ingredients offer a comprehensive solution. Fexofenadine addresses the sneezing, runny nose, and itchy eyes, while Pseudoephedrine focuses on alleviating nasal and sinus congestion. In synergy, Allegra-D starts working in as little as 45 minutes, helping you return to your normal self by improving your symptoms and allowing you to carry on with your daily activities and work4.

"Having Allergies can be downright miserable. At times they can make just getting through the day seem like the biggest hurdle. I have tried many allergy pills that make tons of promises that fail. This product actually gets me through 24hrs and keeps me feeling normal and living my life!"

-  Danielleg170
 Allegra-D® Allergy & Congestion 24 Hour Tablets

Originally posted on influenster.com

What is the Dosage for Allegra-D?

The right dosage ensures that you get the maximum benefits from Allegra-D. Always follow the recommended dosage and consult with a healthcare professional if you are unsure.​​​​​​

For Adults and Children 12 Years and Older:

   Allegra-D 12-hour relief: Take 1 tablet with a glass of water every 12 hours on an empty stomach; do not take more than 2 tablets
in 24 hours
   Allegra-D 24-hour relief: Take 1 tablet with a glass of water every 24 hours on an empty stomach;do not take more than 1 tablet
in 24 hours
   For Children Under 12 Years: do not use.
   For Adults 65 years of age and older: ask a doctor.
   For Consumers with kidney disease: ask a doctor.

**If pregnant or breastfeeding, ask a health professional before use.

Important Notes

  Always swallow the tablet whole. Do not crush, chew, dissolve or break it.
  In case of an overdose, get medical help or contact a Poison Control Center right away.

What are the Safety and Precautions Warnings?


   If you have ever had an allergic reaction to this product or any of its ingredients
   If you are now taking a prescription monoamine oxidase inhibitor (MAOI) (certain drugs for depression, psychiatric, or emotional conditions, or Parkinson’s disease), or for 2 weeks after stopping the MAOI drug. If you do not know if your prescription drug contains an MAOI, ask a doctor or pharmacist before taking this product.
   If you have difficulty swallowing

Ask a doctor before use if you have:

  Heart disease
  Thyroid disease
  High blood pressure​​​​​​​
  Trouble urinating due to an enlarged prostate gland.
  Kidney disease. Your doctor should determine if you need a different dose.

​​​​​​​**If pregnant or breastfeeding, ask a health professional before use.

Where can I get the full product labeling?

  Allegra-D® Allergy & Congestion 24 Hour Tablets
  Allegra-D® Allergy & Congestion 12 Hour Tablets

Remember, while Allegra-D provides effective relief from allergy symptoms, it is crucial to take it responsibly. If you experience any side effects or if your symptoms do not improve, consult with a healthcare professional.

Where can I buy Allegra-D?

Allegra-D® 24-hour and 12-hour tablets are available at pharmacies in most US states without a prescription, except in Mississippi and Oregon, where a prescription is required. Remember, all products that contain pseudoephedrine are being sold behind-the-counter and through interaction with a pharmacist (in line with the US laws and regulations that limit the sale of PSE by pharmacies). To purchase pseudoephedrine a person must:

  1. Present a photo identification card issued by the State or the Federal Government.
  2. The pharmacist will enter your information into a logbook.

Frequently Asked Questions

  • No. Allegra®-D does not include phenylephrine. It's formulated with pseudoephedrine (PSE), a clinically proven ingredient for nasal congestion relief.

  • If you are planning to travel with Allegra-D, be aware of the TSA guidelines. While it is not necessary to present your medication, it is recommended to keep it in your carry-on for easy access5 When traveling internationally, always check the laws regarding OTC medications in your destination country.

    For detailed information on traveling with medications, you can refer to the TSA's guidelines on packing meds.

  • For our sporty readers, it's essential to know that pseudoephedrine has specific guidelines in the athletic world. While it's a champ at clearing up congestion, athletes should be aware of its status in doping regulations. Pseudoephedrine is prohibited "in-competition" only, and athletes are advised to stop taking PSE pills 24 hours before the in-competition period. A concentration of pseudoephedrine in urine greater than 150 micrograms per milliliter is prohibited during competitions6. Always stay informed and play safe!

  • Due to the presence of pseudoephedrine, Allegra-D is sold behind the pharmacy counter. This is in line with federal laws that limit the sale of products containing pseudoephedrine to prevent illegal misuse.

  • How is Allegra-D® different from other allergy medications? What sets Allegra-D® apart is its dual-action formula. While fexofenadine hydrochloride tackles allergy symptoms like sneezing, runny nose, and itchy eyes; pseudoephedrine hydrochloride works to relieve nasal and sinus congestion. This combination ensures comprehensive relief of several allergy symptoms.

  • If you are battling seasonal allergies (hay fever), the combination of fexofenadine and pseudoephedrine ensures that bothersome symptoms are being alleviated, letting you focus on your day instead of your symptoms.

    When given in combination, fexofenadine and pseudoephedrine have complementary activity. Fexofenadine is effective in relieving the symptoms of sneezing, runny and itchy nose, itchy throat, and itchy, watery eyes in patients with seasonal allergies; while pseudoephedrine relieves troublesome symptoms of nasal and sinus congestion.4

    The combination of fexofenadine and pseudoephedrine showed significant improvements in daily activity and work productivity in employed patients, compared to pseudoephedrine alone.4

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Learn More About Allegra-D

Allegra-D 12 Hour Tablets

Get all-day relief from tough allergy and congestion symptoms with Allegra-D® 24 Hour Tablets for adults and children 12 years of age and over.

Learn More

Allegra-D 24 Hour Tablets

Get all-day relief from tough allergy and congestion symptoms with Allegra-D® 24 Hour Tablets for adults and children 12 years of age and over.

Learn More

Allegra® Allergy is here to help.

Life shouldn’t be spent waiting for your allergy symptoms to pass. Allegra® Allergy offers long-lasting (24- and 12-hour), effective, non-drowsy relief for allergy symptoms. Live your greatness and stay on top of symptoms like sneezing, a runny nose, itchy or watery eyes, and nasal congestion or sinus pressure.* 

With a comprehensive range of products, you’re sure to find the one that works best for your indoor and outdoor allergy symptoms. No matter which product you choose, you can feel good knowing Allegra® Allergy is the #1 allergist recommended brand for non-drowsy allergy relief.

Find the Allegra® product that’s right for you

1. Głowacka, K. (2021). Pseudoephedrine—Benefits and risks. International Journal of Molecular Sciences, 22, 5146.

2NHS UK. (2023). Antihistamines. Retrieved September 21, 2023, from https://www.nhs.uk/conditions/antihistamines/

3. Mansfield E. Once-daily immediate-release fexofenadine and sustained-release pseudoephedrine combination: a new treatment option for allergic rhinitis, Expert Opinion on Pharmacotherapy, 2006, 7:7, 941-951.

4. Simpson, J. (2000). Fexofenadine: A review of its use in the management of seasonal allergic rhinitis and chronic idiopathic urticaria. Drugs, 59(2), 301-321.

5. Transportation Security Administration. (2023). Can you pack your meds, pill case, and more questions answered. Retrieved September 21, 2023, from https://www.tsa.gov/travel/travel-tips/can-you-pack-your-meds-pill-case-and-more-questions-answered

6. World Anti-Doping Agency. (2021). TUE physician guidelines – Sinusitis/Rhinosinusitis (Version 2.0). Retrieved September 21, 2023, from https://www.wadaama.org/sites/default/files/resources/files/tue_physician_guidelines_sinusitis_rhin osinusitis.pdf

7. Horak et al. A placebo-controlled study of the nasal decongestant effect of phenylephrine and pseudoephedrine in the Vienna Challenge Chamber. Ann Allergy Asthma Immunol. 2009 Feb;102(2):116-20.

Recommended Reading

*Allegra is indicated to relieve sneezing, runny nose, itchy, watery eyes, and itchy nose or throat. Allegra-D is indicated to relieve sneezing, runny nose, itchy, watery eyes, itchy nose or throat, nasal congestion, sinus pressure, and reduce swelling of the nasal passages.

Among single-ingredient branded OTC oral antihistamines and OTC multi-ingredient allergy & decongestant brands.

This article is not a substitute for medical advice. Allegra should be used as directed according to the product label. If you suspect that you have allergies, consult with your doctor or an allergist. Only they can make a proper diagnosis.