Allegra vs Benadryl

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For patients suffering from allergies, certain drugs that inhibit the body's histamine response can help in managing symptoms such as sneezing, itching, and watery eyes. Allegra and Benadryl are two such medications often recommended for these conditions. Each impacts different aspects of the immune system but both have potential to alleviate allergy symptoms effectively. Allegra (fexofenadine) is a second-generation antihistamine, meaning it doesn't cross the blood-brain barrier as readily as first-generation antihistamines do—this results in fewer side effects like drowsiness. On the other hand, Benadryl (diphenhydramine) is a first-generation antihistamine which may provide faster relief but also has more sedative effects due to its ability to cross into brain tissue more freely.

What is Allegra?

Fexofenadine (the generic name for Allegra) belongs to the second generation of antihistamines, which were a significant advancement from the first-generation antihistamines such as Diphenhydramine (Benadryl). Fexofenadine was first approved by the FDA in 1996. Allegra works by blocking histamine receptors and thus preventing activation of cells by histamine. Unlike many antihistamines, it does not enter the brain from the blood and, therefore, does not cause drowsiness. It is prescribed for relieving hay fever and allergy symptoms, including sneezing; runny or itchy nose; red, itchy or watery eyes; or itching of the throat or roof of the mouth.

On contrary to this Benadryl affects H1 receptors in central nervous system more than fexofenadine which results in common side effects like sleepiness and dry mouth. While both drugs are used to treat allergic reactions, they have different effects on sleep cycle due to their influence on central nervous system.

What conditions is Allegra approved to treat?

Allegra is approved for the treatment of various allergy-related conditions:

  • Seasonal allergic rhinitis, commonly known as hay fever
  • Chronic idiopathic urticaria or hives
  • Skin itching and redness caused by allergies

On the other hand, Benadryl is also used for treating symptoms of allergies but has a broader range of applications including:

  • Allergic reactions to insect bites, stings and certain foods
  • Common cold symptoms
  • Insomnia due to its sedating effect

How does Allegra help with these illnesses?

Allegra (fexofenadine) works to manage allergies by blocking the action of histamine, a chemical substance in the body that is released during an allergic reaction. Histamine causes symptoms such as sneezing, itching, watery eyes, and runny nose. Allegra does this by binding to histamine H1 receptors which prevents them from initiating these allergy symptoms. As an antihistamine, it plays a significant role in managing reactions like hay fever and hives.

On the other hand, Benadryl (diphenhydramine) also works as an antihistamine but has sedative properties due to its ability to cross into the brain more easily than newer generation antihistamines like Allegra. This means while it can effectively control allergy symptoms, it can often result in drowsiness or sleepiness which might not be suitable for everyone.

Therefore, choosing between Benadryl and Allegra will depend on your individual circumstances including how severe your allergies are and whether you need a non-drowsy option.

What is Benadryl?

Benadryl is a brand name for diphenhydramine, which is an antihistamine that works by blocking the effects of histamine, a substance in the body involved in allergic reactions. It was first approved by the FDA in 1946 and has been widely used since then. Benadryl effectively relieves allergy symptoms such as itchy or watery eyes, runny nose, sneezing, itching of the nose or throat, and hives. Unlike newer generation antihistamines like Allegra (fexofenadine), Benadryl also crosses into the brain from the blood and causes drowsiness. This sedative effect can be beneficial when allergies interfere with sleep but could be considered a drawback during daytime use or for individuals who need to stay alert. Other side effects may include dry mouth and difficulty urinating while its impact on cognition might increase risk of dementia over long-term usage especially among older adults.

What conditions is Benadryl approved to treat?

Benadryl has received approval by the FDA for use in treating various conditions, such as:

  • Allergic rhinitis (hay fever)
  • Common cold symptoms
  • Itching or rash due to hives or other allergic reactions
  • Sleep aid to manage short-term insomnia It's important to note that while Benadryl is effective, it may cause drowsiness and should not be used when alertness is needed. Always consult a healthcare provider before starting any new medication.

How does Benadryl help with these illnesses?

Diphenhydramine, the active ingredient in Benadryl, is a chemical that also acts as an antihistamine and plays crucial roles in many processes within the body. It works by blocking histamine receptors to reduce symptoms of allergies such as runny nose, sneezing, itching, and watery eyes. Diphenhydramine has been known for its sedative properties due to its effects on certain parts of the central nervous system. This makes it effective not just for allergy relief but also for aiding sleep. Its multi-faceted action may play a key role in why some patients respond more favorably to Benadryl than non-sedating antihistamines like Allegra (Fexofenadine). However, due to these sedative effects, caution should be exercised when driving or operating machinery after taking Benadryl.

How effective are both Allegra and Benadryl?

Both fexofenadine (Allegra) and diphenhydramine (Benadryl) are established medications for treating symptoms of allergies, but they belong to different generations of antihistamines. Both were approved by the FDA several years apart, with Benadryl being one of the first-generation antihistamines introduced in 1946, while Allegra is a second-generation product that became available in 1996. The two drugs can be prescribed under different circumstances due to their differing side effect profiles.

The effectiveness of both Allegra and Benadryl was directly studied in various trials; both showed similar efficacy in managing allergy symptoms such as sneezing, runny nose and itchy/watery eyes. However, a significant difference lies in their safety profiles. A study conducted back in 2003 found that while both effectively relieved allergy symptoms within an hour or so, patients using diphenhydramine experienced marked sedation - an effect not observed with fexofenadine.

A review on fexofenadine highlights its rapid onset-of-action providing relief from the first dose onwards. It also points out its favorable side-effect profile compared to many other antihistamines; specifically lack of drowsiness making it well-tolerated even among those operating machinery or driving vehicles.

On the other hand, despite being highly effective at relieving allergy symptoms rapidly, diphenhydramine is typically considered a last-resort option due to its sedative properties which can interfere with daily activities like working or driving. This makes it less ideal for continuous use over long periods.

abstract image of a researcher studying a bottle of drug.

At what dose is Allegra typically prescribed?

Oral dosages of Allegra, for adults and children 12 years or older, range from 60 mg twice daily or 180 mg once daily. In comparison, Benadryl's oral dosage can vary drastically depending on the symptoms being treated but generally ranges between 25-50 mg every four to six hours as needed for adults and children over the age of twelve. Children under twelve may be started with lower doses based on their weight (5mg per kilogram). Both medications should not exceed their respective maximum recommended dosages within a 24-hour period.

At what dose is Benadryl typically prescribed?

Benadryl treatment typically begins with a dosage of 25-50 mg every 4-6 hours, not to exceed 300 mg/day. This medication can be taken orally or injected under the skin (subcutaneously), as directed by a healthcare professional. If symptoms persist and there's no response after initial doses, an increase in dose can be considered but should never exceed the maximum limit of 300 mg per day. As always, do ensure that dosages are spaced out appropriately throughout the day for optimal relief from allergy symptoms.

What are the most common side effects for Allegra?

Common side effects of Allegra include:

  • Headache
  • Dizziness
  • Nervousness
  • Diarrhea
  • Cough, upper respiratory tract infection
  • Back or muscle pain

On the other hand, Benadryl has been known to cause:

  • Drowsiness/sleepiness (it's often used as a sleep aid)
  • Dry mouth, nose and throat
  • Dizziness
  • Nausea
  • Vomiting
  • Loss of appetite -Sweating
    These are only some possible reactions and may not occur in every individual. If you experience any severe or persistent symptoms while taking either medication, seek immediate medical attention.

abstract image of a patient experiencing side effect

Are there any potential serious side effects for Allegra?

While both Allegra (fexofenadine) and Benadryl (diphenhydramine) are antihistamines used to treat allergy symptoms, they can have different side effects:

  • Allergic reaction: Although rare, severe allergic reactions like difficulty breathing, swelling of your face or throat may occur. Contact a healthcare professional immediately if you experience any of these symptoms.
  • Cardiovascular issues: While this is generally not common with either medication, in some cases people may experience fast or pounding heartbeats or feel like they might pass out when taking Benadryl. If you experience such symptoms stop using the medicine and seek medical attention quickly.
  • Central Nervous System reactions: Again uncommon but serious side effects include confusion, restlessness, nervousness especially with higher doses of Benadryl.
  • Vision problems: Blurred vision is more often associated with the use of Benadryl due to its anticholinergic properties. Please consult your doctor if you notice any changes in vision while on these medications. Remember that drowsiness and sleepiness are much more common with diphenhydramine (Benadryl), so avoid activities requiring mental alertness such as driving until you know how it affects you.

Always contact your healthcare provider if you experience any unusual side effects after starting a new medication.

What are the most common side effects for Benadryl?

Benadryl, another popular antihistamine medicine, can cause a variety of side effects that people should be aware of. It is known to produce symptoms like dry mouth and stuffy nose which can be uncomfortable for some individuals. Additionally, it may result in blurred vision or ringing in the ears. Gastrointestinal issues such as nausea, vomiting, stomach pain, loss of appetite and constipation are also potential side effects related to Benadryl use. Sleep problems or insomnia might occur due to its sedative properties. Some users have reported feeling anxious or nervous with occasional tremors and sweating. Fast heartbeat could also potentially occur along with confusion or agitation in extreme cases. Skin reactions like rashes are possible while using this medication too. Weight loss isn't commonly associated but has been reported by few users who had prolonged usage of Benadryl; moreover an increase in urination frequency might be noticed although not common either. Lastly, headaches and dizziness are among the more commonly experienced symptoms along with muscle or joint pain occasionally occurring post administration of Benadryl.

Are there any potential serious side effects for Benadryl?

Benadryl, while generally safe and effective for allergy relief, can also cause certain side effects. These might include:

  • Signs of an allergic reaction such as hives; difficulty breathing; swelling of your face, lips, tongue, or throat
  • Dry mouth/nose/throat
  • Drowsiness or dizziness
  • Nausea, constipation
  • Mood changes like restlessness or confusion (particularly in older adults)
  • Blurred vision or trouble focusing

In the event that you experience severe drowsiness accompanied by feelings of weakness and anxiety; a rapid heartbeat/pulse; little to no urination – it is crucial that you stop taking Benadryl immediately and consult with a healthcare professional.

Contraindications for Allegra and Benadryl?

Both Allegra and Benadryl, like most antihistamines, could potentially worsen symptoms in some individuals. If you notice any severe side effects or allergic reactions such as difficulty breathing or swelling of the face, lips, tongue, or throat after taking either of these medications, please seek immediate medical attention.

Neither Allegra nor Benadryl should be taken if you are using monoamine oxidase inhibitors (MAOIs) for depression treatment. Always inform your healthcare provider about all medications and supplements you're currently taking; MAOIs will require a period of about 2 weeks to clear from the system to prevent dangerous interactions with both Allegra and Benadryl. Moreover, due to their sedative properties particularly in case of Benadryl (Diphenhydramine), caution is advised when driving or operating machinery until you know how these drugs affect your alertness level.

How much do Allegra and Benadryl cost?

For the brand name versions of these drugs:

  • The price of 60 tablets of Allegra (180 mg) averages around $35, which works out to approximately $0.58/day.
  • The price of 100 capsules of Benadryl (25 mg) is about $8, working out to approximately $0.08/day.

If you are taking a higher dosage range for Allegra, then Benadryl could be less expensive on a per-day treatment basis. However, cost should not be your primary consideration in determining which drug is right for you.

As far as generic versions go:

  • Fexofenadine (generic Allegra), available in packs starting at 30 tablets and above, has costs ranging from roughly $0.15 to $1 per day depending on the dose and pack size.

-Benadryl’s generic counterpart Diphenhydramine can start as low as about one cent per dose when bought in larger quantities like 100 count bottles. Depending on dosages this could amount up to around ten cents or more per day if multiple doses are required.

Please bear in mind that while generics generally offer significant savings over branded medication, it's always crucial that patients consult with their healthcare provider before making any changes or choices regarding their medications.

Popularity of Allegra and Benadryl

Fexofenadine, in its generic form as well as brand names such as Allegra, is a popular antihistamine and was estimated to have been prescribed to about 4.5 million people in the US in 2020. Fexofenadine accounted for just over 9% of antihistamine prescriptions in the US, sitting comfortably within the top five most commonly used drugs within this class.

Diphenhydramine, including brand versions like Benadryl, was prescribed to approximately 3.2 million people in the USA during that same period. In terms of overall usage within its drug class, diphenhydramine accounts for around 6% of total antihistamine prescriptions across America. The prevalence of diphenhydramine has remained relatively steady throughout recent history.

While both medications are intended for managing allergy symptoms, they differ greatly when it comes to side effects - fexofenadine (Allegra) is a second-generation antihistamine which typically causes less drowsiness than first-generation alternatives like Diphenhydramine (Benadryl). As such, patients needing an effective treatment without substantial sedative effect often prefer fexofenadine over diphenhydramine.


Both Allegra (fexofenadine) and Benadryl (diphenhydramine) are frequently used in the treatment of allergies, backed by numerous clinical studies indicating that they offer relief from symptoms such as itching, runny nose, and sneezing. Both drugs can be used together under certain circumstances but should ideally be administered separately due to their differing mechanisms of action: Allegra is a second-generation antihistamine which selectively inhibits peripheral H1-receptors, while Benadryl is a first-generation antihistamine with central and peripheral effects.

Allegra is often preferred as it causes fewer side effects such as drowsiness or sedation compared to Benadryl. On the other hand, some individuals may benefit from the sleep-inducing effect of Benadryl especially when allergy symptoms disrupt sleep.

Both medicines can be bought over-the-counter without prescription and also come in generic forms, offering cost-effectiveness for patients purchasing out-of-pocket. It's worth noting that both may take some time before noticeable effects occur after initial administration.

While generally well-tolerated; however, users must carefully monitor any adverse reactions. For both drugs, if allergic symptoms persist despite treatment or worsen abruptly medical help should be sought immediately.