Cetirizine Side Effects: Does It Cause Drowsiness?

Table of Contents

• Cetirizine Side Effects Key Facts & Findings
• Side Effects of Cetirizine
• Does Cetirizine Cause Drowsiness?
• A Deeper Analysis: Why Drowsiness May Be Associated with Cetirizine
• Antihistamine Side Effects Comparison Table
• Things You Can do to Manage Drowsiness When Taking Cetirizine
• When to Get Drowsiness Assessed by a Healthcare Professional
• Manage Allergies and Hay Fever With Confidence Using an Award-Winning Online Pharmacy Service by Chemist Click

Cetirizine Side Effects Key Facts & Findings

• Drowsiness affects up to 10% of people who use Cetirizine  
• Dosage, medication, and alcohol can increase sedative effects 
• Cetirizine side effects include sleepiness, headaches, and dizziness

Side Effects of Cetirizine

Cetirizine Side Effects in Adults

Drowsiness and sleepiness are amongst the most common side effects; however there are others to look out for, such as: 

• Headache – tends to occur initially and be mild  
• Dizziness – along with drowsiness, some people can feel lightheaded 
• Dry mouth - can affect saliva production leaving your mouth feeling dry 
• Diarrhoea – can affect and cause changes to bowel movements  

There are several less common side effects, which affect around 1% of people using cetirizine:  

• Extreme tiredness – you may notice you're more tired than usual 
• Skin irritation, Itchy skin, or rash – can be a sign of an allergic reaction  
• Stomach pain – this can be a result of changes to bowel movements 

Side effects may worsen if you take the incorrect dosage. It is important to always follow the advice of your doctor or pharmacist. Some people may need to take a different amount than the typical cetirizine dosage for adults. 

Although very rare, you should seek urgent medical care and call 999 if you or someone you’re with has signs of anaphylaxis, a serious allergic reaction: 

• Sudden swelling of the lips, throat, tongue, or mouth 
• Struggling to breathe, gasping for air, and breathing very quickly 
• Lips or tongue change colour to grey, blue, or pale  
• Sudden dizziness, drowsiness, and confusion  
• Fainting and unable to get up  
• The body is floppy, limp, and not responding  
• A swollen, itchy, blistered, raised, or peeling rash 

You should speak to your doctor or pharmacist if any side effects are affecting you or do not subside. 

Does Cetirizine Cause Drowsiness?

Yes, drowsiness can be caused by cetirizine. 

Every person responds differently to hay fever medicine, regardless of whether it is a drowsy or non-drowsy formulation.  

Non-drowsy medicines are designed to have fewer sedative effects, but this does not 100% rule out drowsiness. Many factors can influence this, such as whether you have taken it before or after drinking alcohol, using other medications or have underlying health conditions.  

A Deeper Analysis: Why Drowsiness May Be Associated with Cetirizine

Histamine influences both allergic reactions and wakefulness.  

Antihistamines block the effects of histamine, and while first-generation medicines such as Diphenhydramine (Benadryl) and Chlorpheniramine can cross the blood-brain barrier, causing drowsiness, newer second-generation types such as Cetirizine (Piriteze) and Loratadine (Claratin) do not, which means they are less likely to cause this.  

However, like with any medication, individual response varies, and it is possible to feel drowsy after taking Cetirizine.  

If you notice a change in your alertness after taking Cetirizine, you may be experiencing side effects. This is usually mild and tends to pass, but if it does not stop or you feel concerned about it you should seek advice from a medical professional. 

Antihistamine Side Effects Comparison Table

Things You Can do to Manage Drowsiness When Taking Cetirizine

If you’re feeling sleepy after taking cetirizine there are things you can try to help: 

• Do not combine other drowsy medications with cetirizine 
• Avoid drinking alcohol – this can increase the sedating effect   
• Try taking cetirizine at night to avoid sleepiness during the day 
• Do not drive or use machinery if you are prone to drowsiness  
• Give it time before you halt medication, most cases pass 

When to Get Drowsiness Assessed by a Healthcare Professional

Drowsiness is common and a temporary side effect for most people. It's usually not a cause for concern, however if you notice that it is persistent and lasts for more than a couple of weeks, it's best to seek advice from a healthcare professional.

Manage Allergies and Hay Fever With Confidence Using an Award-Winning Online Pharmacy Service by Chemist Click

If you’re prone to drowsiness and uncertain whether antihistamine tablets are right for you, our team of UK based pharmacists are on hand to help you find the correct type of hay fever treatment. We offer a wide range of hay fever tablets, as well as nasal sprays for allergies. 

FAQs

Will Cetirizine Make you Sleepy?

Yes, you may feel sleepy after taking cetirizine. Only some people are affected, and it is typically mild. If you find you are feeling sluggish, you can try an alternative medication such as Loratadine or change the time of day that you take it. The evening may be more suitable because any drowsiness will happen whilst you sleep, and you can avoid it during the day.  

How Long Does Cetirizine Drowsiness Last?

If you’re affected by drowsiness, it can take a few hours for it to subside, but this can last for a full day for some people.  

How can you Avoid Drowsiness From Cetirizine?

You may be able to minimise drowsiness from cetirizine by taking it in the evening so that the sedative effects take place whilst you sleep and subside during the day. You should also avoid drinking alcohol, make sure you stay hydrated and stick to the recommended dosage as these can all influence the likelihood of drowsiness.

Sources

• NHS (n.d). Cetirizine. Retrieved 4th February 2025, from: https://www.nhs.uk/medicines/cetirizine/#:~:text=Cetirizine%20is%20classed%20as%20a,These%20may%20contain%20soya%20oil. 

Whilst all of our content is written and reviewed by healthcare professionals, it is not intended to be substituted for or used as medical advice. If you have any questions or concerns about your health, please speak to your doctor.