The Independent Pharmacy

Cetirizine Side Effects: Does It Cause Drowsiness?

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 9 May 2024

Does cetirizine make you drowsy?

Yes, cetirizine can cause sleepiness in some people, though it is generally less sedating than older antihistamine medications. While the potential risk isn’t extremely high, over 1 in 10 people do experience this side effect, according to the NHS. Your individual sensitivity and dosage can impact the likelihood of feeling fatigued.

We understand that drowsiness is an important consideration when choosing a hay fever treatment that won’t disrupt daily activities.

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Cetirizine Tablets & Solution
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So, let’s explore cetirizine’s sedating effects in depth.

Key Takeaways

  • Cetirizine is a modern antihistamine that generally does not cause significant drowsiness in most people, unlike older allergy medications.
  • However, the NHS guidelines on cetirizine state that around 1 in 10 people may experience mild sedation or fatigue as a side effect when taking cetirizine.
  • Other common side effects include dry mouth, headaches, and tiredness, which are typically mild.
  • If excessive, unusual drowsiness occurs, timing doses before bed, staying hydrated, and medical advice from your doctor can help minimise this side effect.

Cetirizine Side Effects

What Are the Common Side Effects of Cetirizine?

Like any medication, cetirizine can potentially cause some adverse effects besides drowsiness. According to the 2023 research, the most common ones include:

  • Dry mouth - This antihistamine can decrease saliva production, leaving you feeling thirsty or with a dry, sticky feeling in your mouth and throat.
  • Headaches - Some people experience headaches, especially when first starting cetirizine. This is usually mild and goes away with time.
  • Fatigue or tiredness - Even if you don't feel drowsy, cetirizine may cause mild fatigue or lack of energy in certain individuals.

These effects are typically mild for most people with hay fever. But as we always remind our customers - if any side effect is really bothersome or persists, don't hesitate to give your healthcare provider a call. They may adjust your dosage or explore other options. You're not alone in this.

Does Cetirizine Make You Drowsy?

Yes, some drowsiness is possible.

The NHS guidelines for cetirizine show that drowsiness occurs in over 1 in 10 people taking cetirizine. So while a majority don’t experience sedation, it’s a notable side effect we can’t ignore, especially if you need to be alert and focused.

The likelihood of feeling drowsy can depend on the dosage as well as your individual sensitivity to antihistamines. Some people simply process the medication differently.

Why? As the NHS explains, antihistamines like Cetirizine work by blocking histamine, the natural chemical responsible for allergic responses like sneezing and itching. However, a 2010 study from the Sleep Medicine Reviews Journal confirms that histamine also plays a role in regulating the sleep-wake cycles in the brain. By blocking histamine’s actions, cetirizine can sometimes cause enough sedation to make you feel drowsy.

Luckily, this drowsiness from cetirizine tends to be milder and shorter-lasting compared to older antihistamine medications. It’s also less likely to severely impair your concentration or coordination for tasks requiring full alertness.

In-Depth Analysis of Cetirizine-Induced Drowsiness

How Cetirizine Causes Drowsiness

To understand why cetirizine can make some people drowsy, we need to look at how it works in the body. Cetirizine is what’s called a second-generation antihistamine (a newer type of hay fever medicine). Compared to older antihistamine medications, it’s designed to cause less sedation.

Here’s the science bit - cetirizine blocks the effects of a natural chemical called histamine. When you have an allergic reaction, your body pumps out extra histamine, causing hay fever symptoms like sneezing, itching, and inflammation. Cetirizine stops histamine from binding to receptors in the body, preventing those symptoms.

But histamine doesn’t just cause the runny nose you get from seasonal allergies. It also plays a role in regulating the sleep-wake cycle in the brain. By blocking histamine, cetirizine can sometimes cause just enough sedation to make you feel a little drowsy.

The good news is that this drowsiness is usually mild and shorter-lasting than older antihistamines. It’s also less likely to impair your coordination or concentration for tasks that require alertness.

Drowsiness Across Different Antihistamines


How likely is it to make you sleepy?



Somewhat likely

A bit more likely to make you sleepy than some similar medicines.

Loratadine (Claritin)

Not very likely

Less likely to make you sleepy compared to Cetirizine.

Fexofenadine (Treathay and Telfast)

Not very likely

Similar to Loratadine, it doesn't usually make you sleepy.

Chlorphenamine (Piriton)

Very likely

Much more likely to make you sleepy; could make daily tasks hard.

Let’s compare cetirizine’s drowsiness potential to some other common antihistamines:

Loratadine (Clarityn) and Fexofenadine (Treathay and Telfast) are very similar – they’re also second-generation antihistamines with a low risk of making you sleepy. In fact, the NHS loratadine guidance suggests they may cause slightly less sedation than cetirizine, with only more than 1 in 100 people experiencing drowsiness.

On the other hand, older antihistamines like Chlorphenamine (Piriton) are much more likely to induce drowsiness and impair your ability to function. These common medications can make driving or operating machinery quite dangerous.

When it comes to choosing an antihistamine, you have to balance effectiveness against the risk of drowsiness and other side effects based on your daily activities and responsibilities. If drowsiness is a major concern, loratadine, fexofenadine, or newer, third-generation antihistamines may be better options to discuss with your doctor.

Managing and Mitigating Drowsiness When Using Cetirizine

Tips to Reduce the Impact of Drowsiness

If cetirizine makes you a bit sleepy, here are some easy tips to help reduce this effect:

  • Timing is key - What's the best time to take the hay fever tablet? Take cetirizine at night before bedtime. That way, any sedative effects can help you sleep better while wearing off by morning. Avoid operating heavy machinery until you know how it affects you. Understanding what affects the pollen count can also help in planning your medication schedules.
  • Stay hydrated - Dehydration can amplify feelings of fatigue from medications. Drink plenty of water throughout the day.
  • Get moving - A bit of light exercise, like walking, can increase alertness and counteract drowsiness. Just be cautious about activities requiring coordination until you know your personal response.
  • Avoid combiners - Don’t mix cetirizine with other sedating (sleep-inducing) drugs or alcohol, as it can make you even sleepier. Give your body’s filter systems a break and read through the NICE's list of cetirizine interactions.
  • Be patient - For some, mild sedation only lasts for the first few days of treatment while the body adjusts. If drowsiness persists beyond 1-2 weeks, let your doctor know.

When to Consult a Healthcare Provider

If you're finding that drowsiness is getting in the way of your daily activities, it's important to talk to your healthcare provider. You deserve to feel your best, and together, we can find a solution that works for you.

Reach out if you experience pronounced fatigue, mental fogginess, slurred speech, or struggle to stay awake and alert even after the tips above. Likewise, any dizziness, loss of coordination, or slow reaction times are red flags.

Severe drowsiness can potentially make routine tasks like driving or operating machinery unsafe. Don’t try to tough it out - let your doctor evaluate if cetirizine is the right option or if a dose adjustment or alternative treatment is needed.

Take the Next Step With The Independent Pharmacy

If cetirizine’s side effects, like drowsiness, are a concern for you, know that you have options. Managing allergies isn’t a one-size-fits-all solution. The team at The Independent Pharmacy understands that each person’s allergic symptoms and medication responses can be different.

That’s why we encourage you to take our online self-assessment. It’s a simple questionnaire that allows you to explain your unique hay fever symptoms, medical history, and any issues you’ve had with current or past medications like cetirizine.

Once you’ve completed the assessment, one of our experts will personally review your responses. They’ll then reach out with tailored treatment suggestions that account for any intolerable side effects while maximising your relief of symptoms.

And if you'd like to learn more about your medical condition, our hay fever guides answer questions you could have when looking for the right antihistamine, such as how long hay fever tablets take to work.

Are you ready to find the right treatment for your hay fever symptoms?

Get in touch with our pharmacists for advice today. We're ready to listen and work together to find a medical treatment - whether you need hay fever solutions for your holiday or everyday activities. Having an ally in your corner can make a world of difference.


Is it better to take cetirizine at night?

For most people with allergies, yes! Taking cetirizine closer to bedtime can help any potential drowsiness that occurs while you’re sleeping. That way, the sedative effects have worn off somewhat by morning.

Can I take cetirizine just to sleep?

No, cetirizine is an antihistamine intended to treat hay fever symptoms, not a dedicated sleep aid. While it may cause drowsiness in some, there are more effective and safer medications specifically for insomnia.

What should I avoid while taking cetirizine?

Avoid driving, operating heavy machinery, or any activities requiring complete mental alertness until you know how cetirizine affects you. Don’t combine it with other sedating drugs or alcoholic beverages, as this increases drowsiness.

Who should avoid cetirizine?

Cetirizine may not be recommended if you have kidney disease or liver disease or take certain medications that could negatively interact. Discuss your complete medical history with a healthcare professional first.

How long does cetirizine stay in your system?

For most people, cetirizine is eliminated from the body within 24 hours after a single dose. However, it can take longer to fully clear in those with kidney problems. Effects like drowsiness may persist until it’s completely out of your system.


NHS (2021). Cetirizine -

NHS (2023). Antihistamines -

Mahesh M. Thakkar (2010). Histamine In The Regulation Of Wakefulness -

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