Xyzal Side Effects: Complete Safety Guide
When Do Side Effects Start? How Long Do They Last? Timeline, Contraindications & Food Interactions
Table of Contents
- Key Takeaways
- What Are the Common Side Effects of Xyzal?
- When Do Xyzal Side Effects Start? (Onset Timeline)
- How Long Do Xyzal Side Effects Last?
- Xyzal Side Effects Timeline: From First Dose to Withdrawal
- Contraindications: When Should You NOT Take Xyzal?
- Food and Alcohol Interactions with Xyzal
- Serious Side Effects and When to Seek Help
- Xyzal Side Effects FAQs
Key Takeaways: Xyzal Side Effects
- Most common: Dry mouth, headache, tiredness, and drowsiness (affect up to 1 in 10 people).
- Onset: Side effects typically begin within the first few hours after taking a dose, correlating with peak blood levels.
- Duration: Most mild side effects resolve within hours to days; drowsiness may last as long as the drug is in your system (half‑life 8‑10 hours).
- Serious risks: Rarely, allergic reactions, seizures, or heart rhythm changes can occur. Stop and seek help immediately if you experience swelling, difficulty breathing, or palpitations.
- Contraindications: Do not take if allergic to levocetirizine/cetirizine/hydroxyzine or if you have severe kidney disease requiring dialysis.
Xyzal (levocetirizine) is generally well tolerated, but like all medicines, it can cause side effects. Understanding what to expect and when helps you manage them effectively.
Important Medical Advice
Stop taking Xyzal and seek immediate medical help if you experience signs of a serious allergic reaction: swelling of the mouth, tongue, face or throat, difficulty breathing, wheezing, sudden drop in blood pressure, or collapse. Also seek urgent advice if you have palpitations, seizures, or severe skin reactions.
What Are the Common Side Effects of Xyzal?
Based on clinical trials and the Patient Information Leaflet, side effects are categorised by frequency.
Common (may affect up to 1 in 10 people)
- Dry mouth – usually mild and transient.
- Headache – can occur but often resolves without intervention.
- Tiredness (fatigue) – a feeling of low energy.
- Somnolence (drowsiness) – sleepiness; occurs in about 8‑10% of users, similar to placebo.
Uncommon (may affect up to 1 in 100 people)
- Exhaustion – more pronounced fatigue.
- Abdominal pain – mild stomach discomfort.
Rare / frequency not known
- Palpitations, increased heart rate
- Seizures (fits), dizziness, syncope (fainting), tremor
- Dysgeusia (distorted taste), vertigo (sensation of spinning)
- Visual disturbances, blurred vision, oculogyration (uncontrolled eye movements)
- Dysuria (painful urination), urinary retention (inability to empty bladder)
- Oedema (swelling), pruritus (itching), rash, urticaria (hives), skin eruption
- Dyspnoea (shortness of breath)
- Weight increase, myalgia (muscle pain), arthralgia (joint pain)
- Aggression, agitation, hallucinations, depression, insomnia, suicidal ideation, nightmare
- Hepatitis, abnormal liver function tests
- Vomiting, increased appetite, nausea, diarrhoea
- Withdrawal pruritus: intense itching upon stopping treatment (even if not present before)
🗒️ Note: This list is not exhaustive. Always consult the patient leaflet or your doctor.
When Do Xyzal Side Effects Start? (Onset Timeline)
Most side effects appear soon after the first dose, typically within 1‑4 hours, which coincides with the peak plasma concentration of levocetirizine. Drowsiness, dry mouth, and headache are often reported during this period. Some effects, like weight gain or liver enzyme changes, may take weeks to become noticeable.
| Side Effect | Typical Onset |
|---|---|
| Drowsiness, dry mouth, headache | 1‑4 hours post‑dose |
| Palpitations, dizziness | First few hours |
| Allergic reactions | Minutes to hours after any dose |
| Weight gain, mood changes | Weeks to months |
| Withdrawal itching | 2‑5 days after stopping |
How Long Do Xyzal Side Effects Last?
Duration varies by the type of side effect and individual factors:
- Mild effects (drowsiness, dry mouth): Usually resolve within 12‑24 hours as the drug is eliminated (half‑life 8‑10 hours). However, with repeated daily dosing, some people may experience persistent mild sedation.
- Withdrawal itching: Can last from a few days to a week. It usually resolves spontaneously but may require restarting treatment under medical supervision.
- Allergic reactions: Resolve after stopping the drug and with appropriate treatment.
- Weight gain, mood changes: May persist as long as the drug is taken; they are reversible upon discontinuation.
Xyzal Side Effects Timeline: From First Dose to Withdrawal
Immediate (first 24 hours)
Onset of common effects: drowsiness, dry mouth, headache. If serious allergic symptoms occur, they also appear rapidly.
First week
Mild side effects may diminish as your body adjusts. Uncommon effects like abdominal pain or exhaustion might appear.
Long‑term use (weeks to months)
Rare effects like weight gain, mood changes, or liver enzyme abnormalities can emerge.
Upon stopping
Withdrawal pruritus (intense itching) may occur within 2‑5 days, even if you never had itching before. This resolves spontaneously or may require restarting treatment.
Contraindications: When Should You NOT Take Xyzal?
Xyzal is contraindicated in the following situations:
- Allergy: Hypersensitivity to levocetirizine, cetirizine, hydroxyzine, or any of the tablet excipients (including lactose).
- Severe kidney disease: Patients with end‑stage renal disease requiring dialysis must not take Xyzal.
- Children under 6 years: The 5 mg tablet strength cannot be adjusted for younger children.
Warnings – consult your doctor before use if:
- You have difficulty passing urine (e.g., spinal cord injury, enlarged prostate).
- You have epilepsy or are at risk of seizures – Xyzal may aggravate seizures.
- You are scheduled for allergy skin testing – Xyzal should be stopped several days beforehand as it may interfere with results.
- You have lactose intolerance – Xyzal contains lactose monohydrate.
Food and Alcohol Interactions with Xyzal
Food: No significant interactions. Xyzal can be taken with or without food. Food may slightly delay absorption but does not affect overall efficacy or side effect profile.
Alcohol: Caution is advised. Although levocetirizine is minimally sedating, alcohol can increase the risk of drowsiness, dizziness, and reduced alertness. Avoid excessive alcohol while taking Xyzal, especially if you need to drive or operate machinery.
Other CNS depressants: Concurrent use with sedatives, hypnotics, or tranquillisers may enhance sedation.
Serious Side Effects and When to Seek Help
Although rare, some side effects require immediate medical attention. Stop Xyzal and contact your doctor or call 111/999 if you experience:
- Signs of allergic reaction: swelling of face, lips, tongue, throat; difficulty breathing; wheezing; sudden drop in blood pressure (feeling faint, collapse).
- Palpitations, irregular or fast heartbeat.
- Seizures (fits).
- Severe skin reactions (widespread rash, blistering).
- Yellowing of skin or eyes (jaundice) – possible hepatitis.
- Suicidal thoughts or self‑harm.
⚠️ Emergency: If you experience any of these, stop the medicine and seek immediate medical help.
Xyzal Side Effects FAQs
Does Xyzal cause drowsiness?
Yes, about 8‑10% of people experience drowsiness, similar to placebo. It is generally mild and may improve with continued use.
Can Xyzal cause weight gain?
Weight increase has been reported rarely. If you notice significant weight gain, consult your doctor.
How long does withdrawal itching last after stopping Xyzal?
Withdrawal pruritus usually appears within a few days and can last from a few days to a week. It often resolves on its own; if severe, your doctor may advise restarting treatment.
Can I drink alcohol while taking Xyzal?
It's best to avoid or limit alcohol, as it may increase drowsiness and dizziness. If you do drink, observe how you feel and avoid driving.
Is Xyzal safe for people with high blood pressure?
Generally yes, as levocetirizine has minimal cardiovascular effects. However, if you have heart disease, consult your doctor before use.
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Clinical References & Sources
Medical Content Manager
Nabeel is a co‑founder and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up‑to‑date.
Medical Doctor
Dr. Feroz is a GMC‑registered doctor and a medical reviewer at Chemist Doctor. He oversees acute condition and urgent care guidance.
Medical Director
Usman is a co‑founder and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 12 March 2026
Next Review: 12 September 2026
Published on: 12 March 2026
Last Updated: 12 March 2026