Levocetirizine + Pseudoephedrine (Xyzal Allergy 24HR): Uses & Side Effects
What it is
Antihistamine + decongestant
A combination antihistamine and decongestant for people who have both allergy symptoms and nasal congestion — effective, but pseudoephedrine carries important cautions around blood pressure and heart rate that make it unsuitable for some people.
This combination product pairs levocetirizine — a third-generation, low-sedating antihistamine — with pseudoephedrine, a sympathomimetic decongestant. Levocetirizine (the active ingredient in Xyzal) blocks histamine H1 receptors to relieve sneezing, runny nose, itchy and watery eyes, and skin itching. Pseudoephedrine works on adrenergic receptors in the nasal blood vessels to constrict them, reducing congestion and opening nasal passages. Together they address both the histamine-driven allergy symptoms and the congestion that antihistamines alone do not reliably relieve. However, pseudoephedrine stimulates the heart and raises blood pressure, which makes this combination inappropriate for certain people — see cautions and contraindications below.
This is a general medication overview, not medical advice or a prescription. A pharmacist or your prescriber can confirm what's right for you.
Key facts
Pseudoephedrine is kept behind the pharmacy counter in the US under the Combat Methamphetamine Epidemic Act — no prescription needed, but ID and purchase limits apply.
Levocetirizine is the R-enantiomer of cetirizine and a third-generation, highly selective peripheral H1-antihistamine with minimal sedation at recommended doses.
Pseudoephedrine raises blood pressure and heart rate; people with hypertension, heart disease, or hyperthyroidism should avoid it or consult their prescriber first.
How Levocetirizine + Pseudoephedrine works
Levocetirizine is the R-enantiomer of cetirizine, a highly selective peripheral H1-antihistamine with very low CNS penetration and minimal sedation. It blocks histamine from binding to H1 receptors in the nose, eyes, and skin, reducing sneezing, itching, and nasal discharge. Pseudoephedrine stimulates alpha-adrenergic receptors in nasal blood vessel walls, causing vasoconstriction that shrinks swollen mucosa and opens the nasal airway. This dual action targets both histamine-mediated allergy symptoms and mechanical congestion.
What it's used for
Levocetirizine + Pseudoephedrine is used to treat the conditions below. This isn't a full list of every off-label use — your prescriber can tell you if it fits your situation.
Seasonal allergic rhinitis accompanied by nasal congestion — hay fever with a blocked or stuffy nose
Perennial (year-round) allergic rhinitis with congestion caused by dust mites, pet dander, or mold
Allergic conjunctivitis — itchy, watery, red eyes alongside nasal symptoms
Urticarial itching combined with nasal congestion in some presentations
Dosage basics
These are general reference points, not a prescription. The right dose depends on your age, other medicines, and health — always follow the product label or your prescriber.
Dosing for levocetirizine and for pseudoephedrine varies by specific product formulation, patient age, weight, and renal function. The label for any combination product specifies the dose and dosing interval. Do not exceed the labeled dose, as pseudoephedrine excess increases cardiovascular and CNS stimulant risks. These are general reference points only — follow the product label and consult your pharmacist or prescriber, especially if you have kidney disease, heart conditions, high blood pressure, or thyroid issues.
Don't start, stop, or change a dose based on this page. Read the label that comes with the product and confirm with a pharmacist or prescriber first.
Side effects to know
Most people tolerate it well, but every medicine has trade-offs. Common effects are usually mild; the serious ones below are rare but need prompt attention.
Usually mild
Common side effects
- Insomnia or difficulty sleeping (pseudoephedrine component — a stimulant)
- Increased heart rate or heart palpitations
- Nervousness, restlessness, or feeling jittery
- Headache
- Dry mouth
- Mild drowsiness (levocetirizine component — less common than with older antihistamines)
Rare — seek care
Serious side effects
- Significant rise in blood pressure — especially a concern for people with pre-existing hypertension
- Rapid, irregular, or strongly pounding heartbeat (tachycardia or palpitations requiring medical attention)
- Difficulty urinating — pseudoephedrine can worsen urinary retention, particularly in men with enlarged prostates
- Signs of hypersensitivity to either component — rash, facial swelling, or difficulty breathing (seek immediate care)
Stop the medicine and get medical help right away for any serious reaction — trouble breathing or fast facial/throat swelling is a 911 emergency.
Interactions & cautions
Some medicines, conditions, and habits change how this drug works — or how safe it is. This isn't exhaustive, so share your full medication list with a pharmacist.
Interacts with
MAO inhibitors (MAOIs) such as phenelzine or tranylcypromine
Combining pseudoephedrine with MAOIs can cause a serious, potentially life-threatening rise in blood pressure. Do not use within 14 days of stopping an MAOI.
Antihypertensive medications (blood pressure drugs)
Pseudoephedrine can reduce the effectiveness of blood pressure-lowering medications and may significantly raise blood pressure. Discuss with your prescriber before combining.
Other stimulants or sympathomimetics, including caffeine
Adds to the stimulant effects of pseudoephedrine — increased heart rate, blood pressure, and nervousness. Limit caffeine while using this combination.
Alcohol and CNS depressants
Levocetirizine is minimally sedating, but alcohol may amplify any drowsiness. Pseudoephedrine's stimulant effect may partially mask alcohol-related impairment — do not rely on this.
Use caution or avoid if
- High blood pressure (hypertension) — pseudoephedrine raises blood pressure and should be avoided or used only under prescriber guidance
- Heart disease, coronary artery disease, or irregular heart rhythm — pseudoephedrine increases heart rate and cardiac workload
- Hyperthyroidism (overactive thyroid) — pseudoephedrine stimulates the same pathways already overactive in thyroid disease
- Narrow-angle glaucoma — sympathomimetics can raise intraocular pressure
- Benign prostatic hyperplasia (enlarged prostate) — pseudoephedrine can worsen urinary retention
- Known allergy to levocetirizine, cetirizine, hydroxyzine, or pseudoephedrine
What most pages leave out
Availability
PrescriptionPseudoephedrine-containing products are kept behind the pharmacy counter in the United States under the Combat Methamphetamine Epidemic Act (2005). You do not need a prescription, but you must show ID and sign a purchase log. Pharmacies limit the quantity you can buy per day and per month.
This covers more than one drug
This product combines two distinct drugs: levocetirizine (the antihistamine component, the same active ingredient as in Xyzal) and pseudoephedrine (a decongestant that shrinks swollen nasal blood vessels). Antihistamines alone often do little for nasal congestion because congestion is not purely histamine-driven — pseudoephedrine is added to address that. However, pseudoephedrine carries its own profile of cardiovascular and stimulant side effects that levocetirizine alone does not. Anyone with blood pressure concerns, heart conditions, or thyroid issues should evaluate whether the decongestant component is safe for them before choosing a combination product over plain levocetirizine.
We flag this so you can make an informed choice — a pharmacist can tell you what's stocked and appropriate where you are.
❓Frequently Asked Questions
Under US federal law (the Combat Methamphetamine Epidemic Act), pseudoephedrine must be sold from behind the pharmacy counter because it can be processed into methamphetamine. You do not need a prescription, but you must present a government-issued ID, and pharmacies record and limit purchases per person. This applies to all products containing pseudoephedrine, including combination allergy-decongestant drugs.
Levocetirizine is a third-generation antihistamine with low CNS penetration, so it is much less sedating than first-generation drugs like diphenhydramine. A small percentage of users do experience mild drowsiness. When combined with pseudoephedrine, a stimulant, the two effects can partially offset each other — but individual responses vary. See how the combination affects you before driving or operating machinery.
You should not take pseudoephedrine-containing products without first consulting your prescriber if you have hypertension. Pseudoephedrine constricts blood vessels throughout the body, which can raise blood pressure and counteract antihypertensive medication. Plain levocetirizine (Xyzal) without pseudoephedrine may be a safer choice for allergy symptoms, and a separate non-drug nasal strategy (such as saline rinses) can help with congestion.
Levocetirizine is the active R-enantiomer of cetirizine, meaning it is the pharmacologically active half of the cetirizine molecule. Some clinical studies suggest levocetirizine provides similar or slightly superior antihistamine effect at a lower dose. In practice, both are effective non-sedating antihistamines for hay fever and hives. Your pharmacist can help you choose based on availability, cost, and your medical history.
No — levocetirizine and pseudoephedrine treat symptoms while you take them but do not change the underlying immune sensitivity to allergens. Allergy immunotherapy, a separate clinician-supervised treatment, is designed to modify the immune response over time and reduce long-term sensitivity. An allergist can advise whether immunotherapy is appropriate alongside or instead of daily symptom management.
Medically reviewed by
Dr. Chet TharpeMD
Last reviewed July 2026
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This content is for general informational purposes only and is not medical advice, a prescription, or a substitute for professional judgment. It does not account for your health, other medications, or dose, and drug information changes over time. Availability, approval status, and formulations differ by country. Always read the product label and ask your pharmacist or prescriber before starting, stopping, or changing any medication. Curex offers at-home allergy testing and immunotherapy for confirmed environmental allergies; it does not sell or provide the medication reviewed on this page and does not provide emergency care.