How do antihistamines cause drowsiness. What are non-drowsy alternatives for allergy relief. How to minimize sedation from allergy medications. When should you take antihistamines to avoid daytime drowsiness. What precautions should you take when using cold and flu medicines with antihistamines.

Understanding the Mechanism of Antihistamine-Induced Drowsiness

Antihistamines are widely used to combat allergy and cold symptoms, but they often come with an unwelcome side effect: drowsiness. To understand why this occurs, we need to delve into the role of histamine in our bodies.

Histamine is a chemical produced by the immune system to fight off allergens and germs. When there’s a threat of allergies or infection, histamine becomes more active, leading to symptoms like runny nose, coughing, sneezing, and itchy eyes. Antihistamines work by blocking the effects of histamine, thus relieving these symptoms.

However, histamine also plays a crucial role in the brain, helping us stay awake and alert. When antihistamines used to treat respiratory symptoms enter the brain, they can interfere with this function, resulting in drowsiness.

The Dual Role of Histamine

• In the immune system: Fights allergens and germs
• In the brain: Promotes wakefulness

Is the drowsiness caused by antihistamines inevitable? Not necessarily. The severity of this side effect can vary depending on the type of antihistamine and individual response.

First-Generation vs. Second-Generation Antihistamines: Drowsiness Comparison

When it comes to antihistamines, not all are created equal in terms of their sedating effects. Understanding the difference between first-generation and second-generation antihistamines can help you make an informed choice about your allergy medication.

First-Generation Antihistamines

First-generation antihistamines, such as diphenhydramine (Benadryl®), are more likely to cause drowsiness. This is because they can easily cross the blood-brain barrier and affect the histamine produced in the brain. While this makes them effective at treating allergy symptoms, it also leads to increased sedation.

Are there any non-drowsy versions of Benadryl® available? Currently, there is no non-drowsy Benadryl® on the market. The sedating effect is inherent to its mechanism of action.

Second-Generation Antihistamines

Newer, second-generation antihistamines like cetirizine (Zyrtec®), fexofenadine (Allegra®), and loratadine (Claritin®) are often marketed as “non-sedating” options. These medications are less likely to cross the blood-brain barrier, resulting in reduced drowsiness for many users.

Which second-generation antihistamine is least likely to cause drowsiness? Among the options, Allegra is generally considered the least sedating.

Strategies to Minimize Drowsiness from Allergy Medications

If you find yourself struggling with drowsiness from your allergy medication, there are several strategies you can employ to minimize this side effect:

1. Opt for second-generation antihistamines
2. Consider nasal spray antihistamines
3. Use intranasal corticosteroids
4. Adjust your medication timing
5. Avoid alcohol consumption

How can nasal spray antihistamines help reduce drowsiness? Nasal spray antihistamines target nasal passages directly rather than circulating throughout your body in the bloodstream. This localized approach can lead to fewer systemic side effects, including drowsiness.

Intranasal corticosteroids are another effective option for reducing reliance on antihistamines. While they may take a few days to start working, they can provide long-term relief with fewer side effects. Some are available over-the-counter, while others require a prescription.

Timing Your Antihistamine Intake for Optimal Results

The timing of your antihistamine intake can significantly impact its sedating effects. To minimize daytime drowsiness, consider taking your antihistamine in the evening rather than in the morning. This approach can help you sleep better while allowing the drowsy effects to wear off by the next morning.

However, it’s important to note that drowsiness from antihistamines can last longer than expected. Some users may experience vivid dreams as a side effect. Be mindful of how your body responds and adjust your medication schedule accordingly.

Tips for Timing Antihistamine Intake

• Take evening doses to minimize daytime drowsiness
• Be aware that drowsiness may persist longer than expected
• Monitor for vivid dreams as a potential side effect
• Adjust timing based on your body’s response

Can taking antihistamines at night improve sleep quality for allergy sufferers? For some individuals, taking antihistamines in the evening may lead to improved sleep quality by reducing nighttime allergy symptoms and leveraging the medication’s sedating effects.

Navigating Cold and Flu Medications Containing Antihistamines

Many people are unaware that cold and flu medications often contain antihistamines, particularly first-generation types. These are included because they are often more effective at treating cold symptoms and drying up runny noses compared to newer antihistamines.

Due to their sedating effects, cold medicines containing antihistamines are typically labeled for nighttime use. It’s crucial to take this labeling seriously, as some medications, like those containing doxylamine, can be even more sedating than others.

Key Points About Cold and Flu Medications

• Often contain first-generation antihistamines
• Labeled for nighttime use due to sedating effects
• Dosages may vary, even within brands
• More is not always better – follow recommended dosages

Why should you avoid combining multi-symptom cold medications with single-ingredient antihistamines? Combining these medications can lead to an overdose of antihistamines, potentially increasing side effects and risks. Always read labels carefully and avoid supplementing multi-symptom medications with additional antihistamines.

Beyond Over-the-Counter Solutions: When to Consult an Allergist

While over-the-counter antihistamines can provide relief for many allergy sufferers, there are situations where professional medical advice is necessary. If your allergy symptoms persist for longer than two weeks or are not adequately controlled with over-the-counter medications, it’s time to consult a board-certified allergist.

An allergist can provide a full diagnosis, identify your specific allergens, and offer personalized treatment plans. They may recommend alternative treatments such as allergen immunotherapy or prescribe non-drowsy allergy medicines that are not available over the counter.

Signs You Should See an Allergist

• Symptoms lasting longer than two weeks
• Inadequate relief from over-the-counter medications
• Severe side effects from current medications
• Need for a comprehensive allergy management plan

What alternative treatments might an allergist recommend for severe allergies? An allergist may suggest allergen immunotherapy (allergy shots or sublingual tablets) to reduce your body’s sensitivity to specific allergens over time. They may also prescribe stronger non-drowsy medications or combination therapies tailored to your specific needs.

Holistic Approaches to Allergy Management

While medications play a crucial role in managing allergy symptoms, a holistic approach can lead to better long-term outcomes. Understanding your specific allergens and taking steps to reduce exposure can significantly impact your quality of life and reduce reliance on medications.

Strategies for Allergen Avoidance

• Use air purifiers with HEPA filters
• Keep windows closed during high pollen days
• Wash bedding regularly in hot water
• Vacuum frequently with a HEPA-filter vacuum
• Use dust-mite-proof covers on pillows and mattresses

How can lifestyle changes complement medical treatments for allergies? Implementing allergen avoidance strategies, maintaining a healthy diet, managing stress, and staying hydrated can all support your body’s natural defenses against allergies. These lifestyle changes, when combined with appropriate medical treatments, can lead to better symptom control and reduced medication dependence.

Remember, the goal of allergy management is not just symptom relief but improving overall quality of life. By understanding the mechanisms behind antihistamine-induced drowsiness, exploring various treatment options, and adopting a holistic approach to allergy management, you can find a balance that works best for you. Always consult with healthcare professionals for personalized advice and treatment plans tailored to your specific needs and circumstances.

When Allergy or Cold Medication Makes You Drowsy

Tips for Staying Alert

By Purvi Parikh, MD

In treating allergies or a cold with antihistamines, you may experience drowsiness, a common side effect of the medication.

How does this happen? Histamine is a chemical produced by the immune system to fight off allergens and germs. When there is a threat of allergies or infection (such as the common cold), histamine is even more active. In its search-and-destroy process, it can cause allergy or cold symptoms such as runny nose, coughing, sneezing and itch eyes. Antihistamine medications relieve these symptoms by blocking the unwanted effects of histamine.

Unrelated to the immune system, histamine is also produced in the brain, where it plays an important part in feeling awake. Antihistamines used to treat respiratory symptoms can get into the brain and interrupt this work, making you feel drowsy.

What can you do about drowsiness from allergy medicines?

Some antihistamines are less likely to cause drowsiness than others. Reactions vary considerably from one person to another. What relieves your symptoms without making you sleepy may be different from what works for someone else.

When you find one that works for you, stick with it – check chemical ingredients and dosages before changing brands or generics. On the other hand, if one doesn’t work for you, try another type.

Does diphenhydramine (Benadryl®) make you sleepy? First-generation antihistamines such as diphenhydramine (Benadryl®) usually cause drowsiness because they are less likely to affect the histamine produced in the brain or have other unwanted effects in the brain. Currently, there is no non-drowsy Benadryl® on the market.

Non-drowsy allergy medicines do exist. Newer, second-generation antihistamines such as cetirizine (Zyrtec®), fexofenadine (Allegra®) and loratadine (Claritin®) – marketed as “nonsedating” – usually cause less drowsiness. An added benefit is that second-generation antihistamines last longer than Benadryl. Allegra is generally the least sedating.

Nasal spray antihistamines are also somewhat less likely to make you sleepy, since they target nasal passages directly rather than sending medicine throughout your body in the bloodstream. These are available only by prescription.

Regular use of an intranasal corticosteroid is not only safe but also an effective way to reduce use of antihistamines. They take a few days to start working, so you need to be patient. Ask your doctor or pharmacist about using an antihistamine with an intranasal corticosteroid the first few days. Some intranasal corticosteroids are available over-the-counter, while others are available as prescription medication.

To avoid daytime drowsiness, take an antihistamine in the evening rather than in the morning. It may help you sleep, with drowsy effects wearing off by the next morning. Be aware that drowsiness can last longer than you might expect – and that some antihistamines can cause vivid dreams.

Don’t drink alcohol when taking antihistamines, as it will increase the sedation.

What about antihistamines in cold and flu medications?

What many people may not know is that cold and flu medicines marketed to treat runny nose and sneezing usually include first-generation antihistamines – the more sedating types. That’s because they are often better at treating cold symptoms and drying up runny nose than the newer types.

Because of their sedating effect, cold medicines with antihistamines are labeled for nighttime use. Take this labeling seriously, as some include medications like doxylamine that are more sedating than others. Check labels for dosages as well, as these may vary, even within brands.

More is not better – read labels carefully and take only as recommended. Don’t supplement a multi-symptom cold medication with another single-ingredient antihistamine.

Be smart, be aware of allergy medication side effects

Smart use of allergy medications – knowing how they treat symptoms of an allergic reaction, being aware of potential unwanted side effects and, most important, monitoring their effect on you and your health – is just one step toward controlling allergy and cold symptoms. Even more important: knowing what you are allergic to and taking steps to prevent or reduce exposure.

If your allergy symptoms tend to last longer than two weeks or are not adequately controlled with over-the-counter medications, schedule an appointment with a board-certified allergist for a full diagnosis.

Antihistamines and intranasal corticosteroids are intended for symptom relief. If antihistamines or intranasal corticosteroids are causing side effects such as drowsiness or other problems, there are other treatment options your doctor can offer for relief from allergic reactions. These options include allergen immunotherapy and non-drowsy allergy medicines like second-generation antihistamines or nasal sprays.

Reviewed by:
Dennis Williams, PharmD, is an Associate Professor at the University of North Carolina Eshelman School of Pharmacy. He practices at UNC Medical Center with the pulmonary medicine medical service. He has served as a member of the National Asthma Education Program Coordinating Committee and the National Asthma Educator Certification Board. He serves on Allergy & Asthma Network’s Board of Directors.

Allegra vs. Zyrtec: How Do They Differ?

We include products we think are useful for our readers. If you buy through links on this page, we may earn a small commission Here’s our process.

Healthline only shows you brands and products that we stand behind.

Our team thoroughly researches and evaluates the recommendations we make on our site. To establish that the product manufacturers addressed safety and efficacy standards, we:

• Evaluate ingredients and composition: Do they have the potential to cause harm?
• Fact-check all health claims: Do they align with the current body of scientific evidence?
• Assess the brand: Does it operate with integrity and adhere to industry best practices?

We do the research so you can find trusted products for your health and wellness.

Read more about our vetting process.

Was this helpful?

Introduction

Sneezing, runny nose, and itchy, watery eyes. This can only mean one thing: allergy season.

Seasonal allergies are typically caused by your body’s reaction to pollen, a substance produced by trees and other plants. When these allergies strike, your body combats them by creating the symptoms you so despise. When these occur, you may consider using an over-the-counter (OTC) medication to ease your symptoms.

Allegra and Zyrtec are two commonly used allergy drugs. Both are available in prescription forms as well, but this article only covers the OTC versions. Here’s a side-by-side comparison to help you decide if one of them is right for you.

The main active ingredient in Allegra is fexofenadine. The main active ingredient in Zyrtec is cetirizine. Both of these drugs are antihistamines.

Antihistamines work by blocking a substance called histamine in your body. Histamine is known for causing allergy symptoms. Blocking it helps prevent symptoms of seasonal allergies or hay fever.

Allegra and Zyrtec are available OTC in many forms. The table below details the forms. For specific dosage information on either drug, read the product package carefully or talk to your doctor or pharmacist.

Allegra and Zyrtec may cause mild side effects that tend to go away as your body gets used to the drug. Most of these don’t call for medical attention. But tell your doctor if any side effects are especially bothersome or don’t go away. Call your doctor or seek medical attention if you experience serious side effects.

The tables below list examples of side effects of Allegra and Zyrtec. Both Allegra and Zyrtec can cause similar side effects. The main difference is that Zyrtec is more likely to cause drowsiness than Allegra.

Drug interactions

If you’re taking other drugs, you should talk to your doctor before using Allegra or Zyrtec. Either one can affect the way the other medications work in your body. These interactions can increase or decrease the effect of the other medications, or of Allegra or Zyrtec. Interactions may also increase your risk of side effects from any drug you’re taking.

Zyrtec may interact with drugs such as theophylline.

Allegra may interact with drugs such as:

• ketoconazole
• erythromycin
• rifampin
• antacids

If you’re taking antacids such as Maalox or Mylanta, take Allegra a few hours before or after you take the antacid. These antacids contain aluminum and magnesium, which can prevent your body from absorbing enough Allegra. This can make Allegra less effective. By taking your antacid at a different time from when you take Allegra, you can reduce this interaction.

Conditions of concern

Allegra and Zyrtec may also not be safe for people with certain health issues. For example, you should talk to your doctor about how safe it is to use Allegra or Zyrtec if you have kidney disease.

If you have liver disease, you should also talk to your doctor before using Zyrtec.

Other warnings

Fruit juices such as grapefruit juice, orange juice, and apple juice can decrease the amount of Allegra that your body absorbs. This can make the drug less effective.

To avoid this interaction, wait at least 4 hours after drinking fruit juice before taking Allegra. Or, you can wait 2 hours after taking Allegra to drink fruit juice. Make sure you take Allegra tablets with water, not juice.

You should also avoid taking Zyrtec and Allegra with alcohol. Combining the drugs with alcohol can cause excessive drowsiness.

Allegra and Zyrtec treat the same symptoms and come in similar forms, but these drugs have a few key differences between them:

• You need to pay attention to what you drink with Allegra because fruit juices can affect how well it works.
• Zyrtec is more likely to cause drowsiness than Allegra.
• The effects of Zyrtec may last a few hours longer than the effects of Allegra.

Your doctor or pharmacist can tell you more about Allegra and Zyrtec and which drug may be right for you. They can also give you advice on taking the drugs safely.

Shop for Allegra.

Shop for Zyrtec.

Allegra and Zyrtec are common over-the-counter drugs used to treat allergy symptoms. Both drugs are safe and effective, but studies show Zyrtec’s effects may last longer than Allegra’s. Zyrtec is more likely to cause drowsiness. Drinking fruit juices can make Allegra less effective.

What and how to treat allergies?

With various allergic symptoms – runny nose, conjunctivitis, urticaria, etc. – we, of course, resort to the help of antihistamines. But at the same time, we rarely think about their features: for example, to which generation this or that remedy belongs, what side effects it has. And it should.

Determining the diagnosis

Let’s start with what is currently known two generations of antihistamines . The first antihistamines began to be used in the 40-50s of the last century. These drugs initially had a number of serious side effects, which, however, did not prevent them from “gaining popularity” – the work on their creation was even awarded the Nobel Prize! ²
Meanwhile, medicine was advancing. In the 1980s, 2nd generation antihistamines appeared. They acted faster, more efficiently and were deprived of a number of side effects. But, nevertheless, many representatives of first-generation antihistamines continue to be widely used, and this despite the fact that reports of undesirable consequences of their use appeared almost 60 years ago! ¹
To this day, we continue to treat allergies with outdated remedies. Out of ignorance or “out of habit” – it doesn’t matter! Agree, if there are more modern and safe drugs, it is unreasonable to use their less successful predecessors, which can harm the health of you and your children.
Still in doubt? Let’s talk in more detail about the dangers of first-generation antihistamines, what advantages second-generation drugs have over them, and which of their representatives should be remembered.

Diagnosis established

“Search and neutralize” ²
Imagine: an allergen enters the body, an allergic reaction begins, during which histamine is released. By binding to receptors, this substance causes swelling, redness of the skin, bronchospasm, difficulty in nasal breathing, so it is very important to block its action, stop the inflammatory reaction.
Histamine receptors are found in blood vessels, smooth muscles, the heart, tissues of the central nervous system, epithelium, and also in the brain. ⁷ In order to relieve allergy symptoms, it is enough to act on peripheral receptors. However, first-generation antihistamines also block receptors in the brain, resulting in a number of side effects:
– They act on the central nervous system, and therefore cause sedation – drowsiness, inhibition of reactions .
– Their action is not stable and durable, which makes it necessary to use high doses several times a day (up to 4-6 times) of these drugs. ( And this despite the fact that the therapeutic concentration is reached only after 2 hours! ³ ) As a result, when using these drugs, there is a possibility of a whole range of side effects: drowsiness, dizziness, lethargy, impaired coordination, inability to concentrate.
– They do not have selectivity (“targeting” action on histamine receptors), they also block other types of receptors, which can cause tachycardia, dryness of the nasopharynx and oral cavity, urinary retention, constipation, and visual impairment. The condition of bronchial asthma may even be aggravated (sputum viscosity increases) and cardiac arrhythmia may occur as a result of toxic effects on the heart. ¹
– May be addictive, and with prolonged (more than 7-10 days) use, the therapeutic activity of the drug decreases.
It is clear that in diseases such as bronchial asthma, chronic urticaria and perennial allergic rhinitis, requiring long-term use of antihistamines, the use of first-generation drugs is highly undesirable. ²
Mistakes we make ¹
Perhaps the biggest mistake of using 1st generation drugs is that many mothers give these drugs to babies before bed at night, hoping that the sedative effect will contribute to a deeper sleep of the child.
In the course of recent studies of the effect of 1st generation antihistamines on the functioning of the brain, it was proved that they cause unnatural sleep, disrupt the course of sleep phases! ¹ The onset of REM sleep (necessary for memory formation and brain development) is delayed, its duration is reduced. The use of first-generation antihistamines often leads to daytime sleepiness, reduced daytime activity, and impaired brain function, which is especially dangerous when they are used in children.

It has also been proven that 1st generation drugs contribute to a significant decrease in the ability of schoolchildren to learn, impaired concentration and memory.
With the regular use of such funds, cognitive functions (the ability of the brain to perceive and process information) are seriously affected, and therefore there is a threat to the full intellectual development of the child.

A special study was conducted in the UK with 1,834 teenage students taking exams. Among the students were those who suffered from allergic rhinitis. They were divided into two groups – those who were not treated with anything, and those who took first-generation antihistamines. For the former, the probability of “failing” the exam was 40%, for the latter – 70%. ¹
In general, it becomes clear why many developed countries are raising the issue of limiting the use of first-generation antihistamines without a prescription. ²
So, if you see one of the following substances on the package or in the instructions, know that you have a 1st generation antihistamine in your hands: Diphenhydramine, chloropyramine, promethazine, dimethindene, clemastine, mebhydrolin, etc. . ²

New generation chooses… ^2.3
What kind of allergy medications do we, modern people, need? Well, of course, those that:
– act quickly and efficiently;
– in therapeutic doses, they practically do not have a sedative effect;
– work even at a high concentration of histamine in the blood, without harming the body;
– suitable for the treatment of most allergic diseases, including chronic forms;
– practically do not affect the ability of children to learn and concentrate;
– contribute to improving the quality of life against the background of the current allergic disease.
It is these qualities that second-generation antihistamines have. These drugs include cetirizine (Zodak®), levocetirizine (Zodak Express®), and fexofenadine (Allegra).
These drugs can also be taken by children. Zodak® in the form of drops can be used in children from 6 months. ⁴ A Zodak® and Zodak Express® tablets are approved for use from 6 years of age. The effect of the drug lasts for 24 hours, so it is taken only once a day. ⁵
In addition, with seasonal allergic rhinitis and chronic urticaria, it is reasonable to prescribe Allegra. It is approved for use in children over 12 years of age and, like Zodak®, is taken only once a day. ⁶
As a conclusion – a small reminder.
For allergies:
– Always consult an experienced allergist;
– Do not be lazy to study this issue yourself. This will allow you to ask the right questions at the doctor’s appointment and understand the essence of the treatment prescribed for your child.