Zyrtec vs Allegra D

Listen to the article instead of reading through it.


For individuals suffering from seasonal allergies or chronic urticaria, certain antihistamines can help manage symptoms and improve quality of life. Zyrtec and Allegra D are two such medications that are commonly used for these conditions. Both work by blocking the effects of histamine, a substance in the body that causes allergy symptoms. However, they differ in their specific actions within the body.

Zyrtec, also known as cetirizine, is a second-generation antihistamine that has a slight tendency to cross the blood-brain barrier and produce sedation. It's typically taken once daily to control allergy symptoms.

On the other hand, Allegra D (fexofenadine) with pseudoephedrine is not only an antihistamine but also contains a decongestant component which makes it more effective in relieving nasal congestion often associated with sinusitis or hay fever. Unlike Zyrtec, it has less potential for causing drowsiness since it doesn’t cross into your brain as much.

What is Zyrtec?

Cetirizine (the generic name for Zyrtec) is an antihistamine that was a significant advancement from the earlier class of first-generation antihistamines. Cetirizine, approved by the FDA in 1995, works by reducing histamine - a natural chemical in the body responsible for allergic responses such as runny nose, sneezing and itching. It's most commonly prescribed to treat symptoms related to hay fever or other upper respiratory allergies.

Fexofenadine and Pseudoephedrine (combined to make Allegra D), on the other hand, are dual-action medications where Fexofenadine serves as an antihistamine like Cetirizine but has less sedative effect while Pseudoephedrine functions as a decongestant which reduces sinus congestion and pressure. The combined medication results in it having broader uses than Zyrtec alone especially when dealing with nasal congestion associated with sinusitis and common cold.

While both drugs have relatively few side effects compared to older generation antihistamines, they differ mainly in their potential for drowsiness – Zyrtec may cause slight drowsiness whereas Allegra D does not typically induce sleepiness due its non-sedating property.

What conditions is Zyrtec approved to treat?

Zyrtec is approved for the treatment of various allergic reactions, including:

  • Seasonal and perennial allergic rhinitis, commonly known as hay fever
  • Chronic urticaria or hives
  • Various symptoms of allergies such as sneezing, runny nose, itchy or watery eyes.

Allegra D on the other hand combines an antihistamine with a decongestant (pseudoephedrine), making it particularly useful for:

  • Treating seasonal allergies in adults and children who are at least 12 years old.
  • Reducing congestion in the nasal passages caused by sinusitis or common colds along with allergy management.

It's important to note that Allegra D should not be used by patients with high blood pressure, glaucoma or severe coronary artery disease without medical guidance due to its pseudoephedrine component.

How does Zyrtec help with these illnesses?

Zyrtec helps manage allergies by blocking the action of histamine, a substance in the body that is released during an allergic reaction. It does this by occupying the receptors that histamine binds to, thus preventing it from triggering symptoms such as sneezing, itching, runny nose and watery eyes. Histamine is an organic nitrogenous compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Allergic reactions trigger the release of histamine causing inflammation and irritation. By blocking these effects with Zyrtec's active component cetirizine hydrochloride, it can limit discomfort caused by such allergy symptoms.

On other hand Allegra D combines two medications: fexofenadine (an antihistamine) to reduce sneezing and hives; pseudoephedrine (a decongestant) to relieve stuffy or blocked nose. The combination provides more comprehensive symptom relief for those suffering from seasonal allergies.

What is Allegra D?

Allegra D, also known by its generic name fexofenadine/pseudoephedrine, is an antihistamine and decongestant combination. It operates by blocking histamines in the body and narrowing blood vessels to decrease swelling and congestion. Fexofenadine was first approved by the FDA in 1996 as a second-generation antihistamine that does not penetrate the brain from the blood; thus it causes less drowsiness than first-generation antihistamines.

Unlike Zyrtec (cetirizine), Allegra D does not cross into the brain from the bloodstream significantly, meaning there are fewer side effects such as sedation or interference with cognitive function. This makes Allegra D a preferred choice for those who require allergy relief without feeling tired or impaired during their daily activities. However, it does contain pseudoephedrine which can cause restlessness or insomnia in some users - this is why it's typically recommended for daytime use rather than before bed.

What conditions is Allegra D approved to treat?

Allegra D is a widely used antihistamine and decongestant combination, approved by the FDA for managing:

  • Seasonal allergies (hay fever)
  • Chronic idiopathic urticaria (hives not caused by other health conditions) In addition to relieving symptoms like sneezing, runny nose, itchy or watery eyes, itching of the nose or throat due to hay fever or other upper respiratory allergies. The 'D' in Allegra D stands for decongestant which helps with congestion from these allergenic reactions.

How does Allegra D help with these illnesses?

Pseudoephedrine is a decongestant which acts similarly to adrenaline, a hormone and neurotransmitter. It constricts blood vessels in the nasal passages, leading to reduced inflammation and congestion. Combined with fexofenadine, an antihistamine similar to cetirizine (Zyrtec), it forms Allegra D. This combination works effectively on multiple symptoms of allergies including runny nose, sneezing, itchy or watery eyes, hives, skin rash and itching. As compared to Zyrtec alone that primarily addresses histamine-related allergy symptoms such as itching and redness of eyes or skin rashes; Allegra D expands its action not only by blocking the effects of histamine but also by reducing nasal congestion due to common cold or allergies. Therefore it may be preferred when patients are experiencing combined symptoms or during certain times of year when these conditions tend to worsen.

How effective are both Zyrtec and Allegra D?

Both cetirizine (Zyrtec) and fexofenadine with pseudoephedrine (Allegra D) are popular choices when it comes to over-the-counter antihistamines, frequently used for relieving symptoms of allergies. They were both approved by the FDA within a few years of each other in the mid-1990s. While they act on similar receptors in the body, their compositions differ which may lead them to be selected under different circumstances.

The effectiveness of Zyrtec and Allegra D was compared directly in a double-blind clinical trial conducted in 2001; both drugs demonstrated comparable efficacy in alleviating allergy symptoms such as sneezing, itchiness and runny nose. In this study, none of the metrics studied to measure efficacy differed significantly between patients receiving Zyrtec or Allegra D.

A review done on cetirizine showed that it starts working quickly - often within an hour after taking a dose – providing rapid relief from allergy symptoms. The side effect profile is also favorable; while drowsiness can occur, it is generally less pronounced than some older antihistamines. A key point about cetirizine is its ease-of-use - one dose lasts 24 hours so no need for multiple doses throughout the day.

On the other hand, fexofenadine with pseudoephedrine (Allegra-D), combines two active ingredients: an antihistamine for treating allergic reactions and nasal congestion caused by inflammation along with a decongestant component designed to relieve sinus pressure and congestion specifically. This makes Allegra-D particularly effective at tackling more severe cases where these additional symptoms are present but might not be needed if you only have mild allergies or hay fever without significant nasal congestion.

abstract image of a researcher studying a bottle of drug.

At what dose is Zyrtec typically prescribed?

Oral dosages of Zyrtec range from 5-10 mg/day for adults and children over the age of six, with studies suggesting that a daily intake of 10 mg is sufficient in relieving symptoms like runny nose, sneezing, itchy or watery eyes. For children between two to five years old, the recommended dosage starts at 2.5 mg per day. In either population, dosage can be increased after one week if there's no response. The maximum dosage that should not be exceeded in any case is 10 mg/day.

On the other hand, Allegra D has different strengths: fexofenadine/pseudoephedrine 60mg/120mg respectively for twice-daily administration; or fexofenadine/pseudoephedrine 180mg/240mg for once daily dose. It's crucial to follow doctor’s instructions when using this medication due to its decongestant properties which might cause side effects if misused.

At what dose is Allegra D typically prescribed?

Treatment with Allegra D typically begins at a dosage of 60 mg/120 mg (fexofenadine/pseudoephedrine) taken by mouth once or twice a day. The dose can be increased to 180 mg/240 mg, divided into two doses, spaced approximately 12 hours apart if symptoms persist. The maximum recommended daily dose is 180 mg/240 mg divided into two doses of fexofenadine/pseudoephedrine and spaced around 12 hours apart. This may be tested if there's no significant response to the initial treatment after sufficient time has passed. As always, it's important that patients take medications as directed by their healthcare provider.

What are the most common side effects for Zyrtec?

Side effects of Zyrtec and Allegra D can vary significantly due to their different active ingredients. Common side effects of Zyrtec (Cetirizine) include:

  • Drowsiness or fatigue
  • Dry mouth
  • Stomach pain, nausea or diarrhea
  • Headache

On the other hand, Allegra D (Fexofenadine and pseudoephedrine) is known to cause:

  • Nervousness or restlessness
  • Difficulty sleeping (insomnia)
  • Increased heart rate
  • Headaches -Dry mouth, coughing -Stomach discomfort.

It's also important to note that each individual may react differently to these medications. Always consult your healthcare provider for advice on medication choices.

abstract image of a patient experiencing side effect

Are there any potential serious side effects for Zyrtec?

Both Zyrtec and Allegra D are antihistamines used to relieve allergy symptoms, but they can cause different side effects in some patients. With Zyrtec, rare yet serious side effects could include:

  • An allergic reaction: rash; itching/swelling (especially of the face/tongue/throat); severe dizziness; trouble breathing
  • Difficulty urinating or an inability to urinate
  • Changes in vision

Allegra-D, on the other hand, may lead to these infrequent but grave adverse reactions:

  • Racing or irregular heartbeat
  • Mood changes such as confusion, extreme restlessness, hallucinations
  • Trouble sleeping
  • Ringing in the ears

It's important to note that these medications contain decongestants which could potentially raise your blood pressure. Hence those with hypertension should be cautious while using them. If you notice any of these symptoms after starting either medication, seek immediate medical attention.

What are the most common side effects for Allegra D?

Allegra D, an effective antihistamine and decongestant combination, can sometimes cause side effects such as:

  • Dry mouth or throat
  • Nausea or upset stomach
  • Sleep problems (insomnia)
  • Dizziness, nervousness or restlessness
  • Headache
  • Increased heart rate due to the decongestant component
  • Ringing in the ears

Some users might experience a rash, although this is less common. It's also worth noting that unlike some other allergy medications, Allegra D doesn't typically result in weight loss and isn't known for causing blurred vision. Remember though that individual reactions can vary widely – if you notice any unusual symptoms after starting Allegra D, it's important to consult with your healthcare provider promptly.

Are there any potential serious side effects for Allegra D?

While Allegra D is generally well-tolerated, it can sometimes cause serious side effects. If you experience any of the following symptoms after taking Allegra D, seek medical attention immediately:

  • Signs of an allergic reaction such as hives; difficulty breathing; swelling of your face, lips, tongue or throat
  • Rapid heartbeat or fluttering in your chest
  • Confusion and feeling like you might pass out
  • Increased blood pressure with severe headache, blurred vision, buzzing in your ears, anxiety and/or confusion
  • Abnormal behavior changes such as restlessness or nervousness (more likely to occur in children)

It's crucial to note that this is not a complete list of potential side effects. Always discuss possible risks and benefits with your healthcare provider before starting new medication.

Contraindications for Zyrtec and Allegra D?

Both Zyrtec and Allegra D, like most antihistamine medications, may worsen symptoms such as drowsiness in some people. If you notice your symptoms worsening or if you experience an increase in side effects such as dry mouth, constipation, or difficulty urinating please seek immediate medical attention.

Neither Zyrtec nor Allegra D should be taken if you are taking, or have been taking monoamine oxidase (MAO) inhibitors (MAOIs). Always tell your physician which medications you are taking; MAOIs will require a period of about 2 weeks to clear from the system to prevent dangerous interactions with Zyrtec and Allegra D. Also note that because both these drugs contain decongestants they can cause potential problems for individuals with certain health conditions such as high blood pressure, glaucoma and heart disease. Therefore it is important to consult with your doctor before starting either medication.

How much do Zyrtec and Allegra D cost?

For the brand name versions of these drugs:

  • The price of a 30-tablet package of Zyrtec (10 mg) averages around $18, which works out to approximately $0.60/day.
  • The price of a 20-tablet package of Allegra-D (60 mg) is about $25, working out to roughly $1.25/day.

Thus, if you are using either drug as recommended (i.e., one tablet per day), then brand-name Zyrtec is less expensive on a per-day treatment basis. Please note that cost should not be your primary consideration in determining which medication is right for you.

For the generic versions of Zyrtec (cetirizine) and Allegra D (fexofenadine with pseudoephedrine):

  • Cetirizine can be bought in packs ranging from 30 tablets up to more than 300 tablets. A pack costs between $10 and $15 for 30 tablets depending on where it's purchased, resulting in an approximate daily cost as low as $0.33-$0.50.
  • Fexofenadine with pseudoephedrine comes typically available in packs ranging from 15 tablets up to more than100 tablets; the price ranges from about$12-$20 for a box containing15 pills or approximately$0.80 - $1/33 per day.

Remember that while both medications are used for similar purposes like relieving allergy symptoms, their side effects may differ due to the presence of decongestant pseudoephedrine in Allegra D but not in Zyrtec so do consider this along with cost while choosing between them.

Popularity of Zyrtec and Allegra D

Cetirizine, also known by the brand name Zyrtec, was estimated to have been used by approximately 12 million people in the US in 2020. Cetirizine accounted for nearly 15% of over-the-counter antihistamine purchases and usage in America. As an effective second-generation antihistamine, cetirizine is often sought after due to its long-acting nature that provides all-day relief from allergy symptoms.

Fexofenadine with pseudoephedrine, better known as Allegra D, was utilized by about 5 million people within the same year. In terms of combination decongestant and antihistamine medications available without a prescription, it accounts for just under 10% of overall usage. The prevalence of Allegra D has remained relatively steady over the past decade. This drug serves a dual purpose: fexofenadine acts as an antihistamine while pseudoephedrine works as a nasal decongestant providing relief for stuffy noses alongside typical allergy symptoms.


Both Zyrtec (cetirizine) and Allegra D (fexofenadine with pseudoephedrine) are widely used in the management of allergy symptoms, and both have been proven effective through numerous clinical studies. They work similarly by blocking histamine receptors to reduce allergic reactions, but they also differ in their composition and effects. Zyrtec is an antihistamine alone, while Allegra D combines an antihistamine with a decongestant.

In terms of efficacy, both drugs are potent against symptoms like sneezing, itching, runny nose and watery eyes associated with seasonal allergies or hives. However, the added pseudoephedrine in Allegra D gives it a particular effectiveness against nasal congestion.

Zyrtec is available as a generic drug which can significantly save costs for patients who pay out-of-pocket. On the other hand, because of its dual-action formula that includes a decongestant along with an antihistamine, Allegra D may be more expensive than Zyrtec.

Side-effects between these two medications vary: drowsiness tends to occur more frequently with Zyrtec than with Allegra-D due to cetirizine's tendency to cross into the brain; however this side effect typically decreases over time once your body adjusts to the medication. Conversely being non-drowsy ,Allegra-D might cause insomnia due to its pseudoephedrine content.

It’s important that patients closely monitor any reactions when starting treatment on either drug and report any adverse side effects immediately so healthcare providers can adjust prescriptions accordingly.