Is Zyrtec or Benadryl better for hives

Benadryl Vs. Zyrtec: What Is The Difference?

Aug 10, 2018

Sami asked

Can you let me know how Benadryl and Zyrtec are different? What characteristics separate them?

At a glance

• There are several differences between Zyrtec and Benadryl, even though they are both antihistamines.
• Most notably, Benadryl is a 'first-generation' antihistamine, which are known to cause sedation. Zyrtec is a 'second-generation' antihistamine and has a lower risk of sedative effects.
• Additional differences between the two include how long they last per dose and what they can be used for.

Answer

While Benadryl (diphenhydramine) and Zyrtec (cetirizine) are both classified as antihistamines, there are significant differences between them, including:

• Classification
• Dosing
• Indications
• Effectiveness
• Side Effects

Below, we discuss each of these differences in detail and provide information to help you decide which will be best for you in a given situation.

Benadryl Vs. Zyrtec: Classification

Antihistamines are grouped largely by their 'generation' in regard to the time in which they were developed and made commercially available.

Benadryl is a 'first-generation' antihistamine in the ethanolamine class of drugs. 'First-generation' antihistamines are typically associated with:

• A relatively short duration of action (around 4-12 hours).
• Significant sedative and anticholinergic effects.

Zyrtec is a "second-generation" antihistamine in the piperazine class of drugs. They are structurally related to ethanolamines but have a:

• Longer duration of action (12-24 hours).
• Low to moderate sedative and anticholinergic effects.

Benadryl Vs. Zyrtec: Dosing

How each is dosed shows significant differences in the duration of action of each.

Benadryl

Benadryl has a duration of action of around 4 to 6 hours, although this can be prolonged in those with liver disease or in the certain populations like the elderly. In addition, some individuals can be 'slow-metabolizers' or 'fast-metabolizers' of Benadryl, which alters how long the effects last for.

Benadryl is typically dosed at 25 to 50 mg at 4 to 6 hour intervals.

Zyrtec

Zyrtec has a duration of action of 24 hours, which is the claim to fame of most 'second-generation' antihistamines. This long duration of action allows it to be dosed only once a day, which is ideal for treating perennial and seasonal allergy symptoms.

The most common dose of Zyrtec is 10 mg once daily, although low doses of Zyrtec twice daily can be used in young children for certain indications, like atopic dermatitis (i.e. eczema).

Benadryl Vs. Zyrtec: Indications

Both Benadryl and Zyrtec can be used to treat allergy symptoms. When it comes to seasonal or perennial allergies, Zyrtec is more often preferred due to its longer duration of action.

Other than your run-of-the-mill allergy symptoms, both can be effective for:

• Runny nose
• Watery eyes
• Urticaria (hives)
• Itching
• Dermatitis

In addition to the above, Benadryl is commonly used as an over the counter sleep aid, due to its sedative effects and short duration of action. In fact, diphenhydramine is an active ingredient in many over the counter products marketed for sleep including ZzzQuil.

Lastly, it comes to allergic reactions (e.g. drug induced), there is some controversy in regard to which is more effective.

This is discussed in the next section but it should be noted that Benadryl still hold preferential treatment for most allergic reactions.

This is best exemplified by the ACIP (Advisory Committee on Immunization Practices) recommendations to use diphenhydramine (active ingredient in Benadryl) for vaccine induce anaphylaxis, although the specific recommendation is injectable diphenhydramine.

Benadryl Vs. Zyrtec: Effectiveness

Both Benadryl and Zyrtec have shown comparable activity and efficacy when it comes to the treatment of allergic symptoms, and choice of either is typicality based on patient preference and desired characteristics (e.g. duration of action) .

It is commonly thought that 'first-generation' antihistamines like Benadryl are more effective for allergic reactions (e.g. bee stings, drug related, food related) than newer agents, but a variety of studies have reported that Zyrtec not only has similar efficacy, but it also works just as fast.

A popular and informative way antihistamines are tested is by inducing a 'wheal and flare' reaction in an individual via an injection of histamine and measuring response to a given drug in terms of relief of inflammation, redness and itching. Zyrtec consistently produces results comparable to Benadryl.

For the treatment of atopic dermatitis (i.e. eczema), results from studies are mixed. Efficacy is similar between Zyrtec and Benadrylbut Benadryl certainly has more published evidence.

It is important to note that Zyrtec is used 'off-label' for atopic dermatitis while Benadryl is FDA approved for the symptomatic treatment of it.

Benadryl Vs Zyrtec: Side Effects

Perhaps the biggest difference between Benadryl and Zyrtec is the side effect profile of each.

Benadryl is well known to cause both sedation and somnolence. Zyrtec on the other hand, being a 'second-generation' antihistamine, is less associated with sedation. While most second-generation antihistamines (e.g. Claritin) are in fact 'non-drowsy', Zyrtec is not labeled as such, but produces far less sedation than Benadryl.

Multiple studies have reported that Benadryl, when compared to antihistamines like Zyrtec, is more strongly associated with:

• Sedation
• Drowsiness
• Decreased mental performance
• Decrease motor performance
• Decreased ability to concentrate

Per the prescribing information for Zyrtec, the overall incidence of sedation and somnolence is around 10-15%. Benadryl causes sedation in more than 20-30% of individuals. The doses of Benadryl used for sleep (50 mg) cause an even higher incidence.

Lastly, due to stronger anticholinergic effects, Benadryl is also associated with a slightly higher incidence of:

• Dry mouth
• Dry eyes
• Constipation
• Heart palpitations (high doses)
• Respiratory depression (high doses)

Final Words

Choosing between Benadryl and Zyrtec depends on what you are looking for in either drug.

For consistent allergy symptoms, Zyrtec is likely the better choice due to its long duration of action and lower incidence of sedation. For the treatment of insomnia, Benadryl is likely more effective due to its strong sedating effects.

For allergic reactions to food and drugs, evidence is mixed. Zyrtec may be just as beneficial as Benadryl and offer a lower risk of side effects. This is a more commonly accepted use of Benadryl however and it is the recommended agent of choice for vaccine induced allergic reactions (via IM injection).

Let us know which antihistamine you prefer and your experiences with them in the comment section below!

Comparing Benadryl vs. Zyrtec for Allergy Relief

1. Mechanism of Action

Antihistamines like Benadryl and Zyrtec work by blocking the effects of histamine, a chemical released during allergic reactions. However, critical differences in their mechanisms of action impact their safety and side effect profiles.

Benadryl

Benadryl is an antihistamine that belongs to the first-generation antihistamine class. The primary mechanism of action of diphenhydramine involves blocking the effects of histamine, a natural chemical produced by the body in response to allergens. Histamine is responsible for triggering symptoms during allergic reactions such as:

As a first-generation antihistamine, Benadryl readily crosses the blood-brain barrier and acts on central nervous system (CNS) histamine receptors. By binding to and inhibiting these receptors, diphenhydramine mitigates the effects of histamine in the brain, leading to its sedative and drowsiness-inducing properties. This CNS depression is why Benadryl is often used not only for allergies but also for its sedative effects in treating insomnia and motion sickness.

Moreover, Benadryl exhibits anticholinergic properties, blocking the action of acetylcholine, another neurotransmitter. This contributes to its side effects, such as dry mouth, constipation, and blurred vision.

Zyrtec

Zyrtec is a second-generation antihistamine, and its primary active ingredient is cetirizine. Unlike first-generation antihistamines like Benadryl, cetirizine has a more selective action on peripheral H1 receptors, primarily located in the tissues rather than the CNS. This results in reduced penetration of cetirizine into the brain, leading to a lower incidence of sedation and drowsiness compared to first-generation antihistamines.

The main mechanism of action of Zyrtec involves blocking the effects of histamine at the peripheral H1 receptors. By inhibiting histamine binding, cetirizine prevents or alleviates allergy symptoms, including:

• Sneezing
• Itching
• Runny nose

Cetirizine does not readily cross the blood-brain barrier significantly, reducing the likelihood of sedative effects. While it may still cause mild drowsiness in some individuals, this is generally less pronounced than first-generation antihistamines.

2. Efficacy In Treating Allergy Symptoms

A study found that Zyrtec and Benadryl displayed comparable efficacy and onset of action, with the added benefit of Zyrtec having a longer duration of action. This implies that Zyrtec may provide sustained relief over a longer period than Benadryl.

Additionally, a literature review comparing Benadryl to non-sedating antihistamines, such as Zyrtec, emphasized that all antihistamines shared similar effectiveness. However, the review highlighted a key advantage of newer antihistamines like Zyrtec, which is their tendency to cause less sedation compared to traditional options like Benadryl.

The Canadian Society of Allergy and Clinical Immunology (CSACI) recommendations further support the preference for Zyrtec over Benadryl. According to the CSACI, newer antihistamines like Zyrtec are considered safer, less sedating, and more effective. They caution against the potential side effects associated with Benadryl, including sedation, impaired sleep, and motor impairment, which could lead to accidents and, in extreme cases, even death. The CSACI suggests that Benadryl should only be utilized as a last resort.

3. Dosage and Administration

Proper dosage is key for antihistamines to provide effective allergy relief while minimizing side effects.

Benadryl

Benadryl is available in various forms, such as:

For adults and children aged 12 years and older, the usual dose ranges from 25 to 50 mg every four to six hours, as needed. It can be taken with or without food, but some may take it primarily at bedtime due to its potential to cause drowsiness.

For children under 12 years, the specific weight-based dose should be determined in consultation with a healthcare provider.

The liquid form should be measured using the dosing syringe or a special dose-measuring device. Motion sickness may be addressed by taking Benadryl 30 minutes before the triggering situation, and as a sleep aid, it is recommended within 30 minutes before bedtime.

In case of a missed dose, it can be taken as soon as remembered. However, extra medicine is not advised to make up for a missed dose.

Zyrtec

Zyrtec is available in tablets and liquid.

For adults and children 6 years and older, the standard dose is 10 mg once daily, with the option to take it with or without food.

Children aged 6 months to 2 years may start with an initial dose of 2.5 mg once daily, with a maintenance dose of 2.5 mg once to twice daily, not exceeding 5 mg daily. For children aged 2 to 5 years, the initial dose is 2.5 mg once a day, with a maintenance dose of 2.5 mg twice a day or 5 mg once daily, with a maximum of 5 mg per day.

For children aged 6 years and older, the dose is 5 to 10 mg once a day, not exceeding 10 mg per day.

Zyrtec can be taken with or without food; chewable tablets should be chewed before swallowing. Orally disintegrating tablets should be allowed to dissolve in the mouth without chewing.

If a dose is missed, skipping it rather than two doses at once is recommended.

4. Side Effects

While antihistamines treat allergies, they may prompt side effects ranging from mild to severe.

Benadryl

Common side effects of Benadryl may include:

• Dizziness
• Drowsiness
• Loss of coordination
• Dry mouth, nose, or throat
• Upset stomach
• Constipation
• Dry eyes
• Blurred vision
• Daytime drowsiness or a "hangover" feeling after nighttime use

More severe side effects that require immediate medical attention consist of signs of an allergic reaction, such as:

• Hives
• Difficulty breathing
• Swelling of the face, lips, tongue, or throat

Contacting a doctor is necessary if experiencing:

• Pounding heartbeats or fluttering in the chest
• Painful or difficult urination
• Little or no urination
• Confusion
• Feeling like they might pass out
• Tightness in the neck or jaw with uncontrollable movements of the tongue