Loratadine (Claritin): Uses, Dosage & Side Effects
What it is
Second-generation antihistamine
Loratadine (Claritin) is a widely available, once-daily non-sedating antihistamine for hay fever and hives — FDA-approved and sold over the counter. Omeprazole (Prevacid 24HR) is a separate, unrelated acid-reflux drug that was paired with it on a prior page in error.
Loratadine is one of the most commonly used second-generation antihistamines. It blocks H1 histamine receptors to relieve sneezing, runny nose, itchy eyes, and hives caused by allergens. It is non-sedating at standard doses, taken once daily, and available over the counter throughout the United States under the brand name Claritin and as generics. This page also addresses omeprazole (the proton pump inhibitor sold as Prevacid 24HR or as generics): omeprazole reduces stomach acid and is used for heartburn and acid reflux. It has no allergy-related action and was paired with loratadine on a prior content page by an automated tool. The two drugs are unrelated and treat entirely different conditions.
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
Loratadine (Claritin) is an FDA-approved, over-the-counter second-generation antihistamine — one of the most widely used allergy medications in the United States.
Omeprazole (Prevacid 24HR uses lansoprazole) is a proton pump inhibitor for acid reflux — an entirely different drug class with no role in allergy treatment.
Second-generation antihistamines like loratadine have significantly lower CNS penetration than first-generation agents, producing little sedation at standard doses.
How Loratadine works
When the immune system encounters an allergen — pollen, pet dander, mold — it releases histamine. Histamine binds to H1 receptors throughout the body, causing sneezing, itching, runny nose, and hives. Loratadine is a selective peripheral H1-receptor antagonist: it competes with histamine at those receptors and blocks the allergic response. Because it does not readily cross into the brain, it causes little to no drowsiness at the standard dose.
What it's used for
Loratadine 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 (hay fever) — sneezing, runny and itchy nose, watery eyes
Perennial (year-round) allergic rhinitis caused by indoor allergens such as dust mites and pet dander
Chronic idiopathic urticaria (persistent hives) and itching
Allergic conjunctivitis — itchy, red, watery eyes
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.
The standard adult and adolescent dose of loratadine is 10 mg once daily — this is the amount in one standard Claritin tablet or equivalent generic. It can be taken with or without food. Children's dosing is weight-based and varies by product; follow the label for pediatric formulations. These are general reference figures only — defer to the product label and your pharmacist or prescriber for your specific situation, especially for children, older adults, and those with kidney or liver impairment.
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
- Headache
- Dry mouth
- Fatigue or mild drowsiness (uncommon at standard 10 mg dose)
- Nausea or stomach upset
- Nervousness (reported rarely, more often in children)
Rare — seek care
Serious side effects
- Hypersensitivity reaction to the drug itself — hives, rash, swelling of the face or throat, difficulty breathing (seek immediate care)
- Rapid or irregular heartbeat (rare; report to your clinician)
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
Ketoconazole and certain azole antifungals
May increase loratadine blood levels by inhibiting its metabolism. Standard doses are generally well tolerated but inform your pharmacist.
Erythromycin and similar macrolide antibiotics
Can elevate loratadine levels. At standard doses this has not been clinically significant in studies, but it is worth flagging to your prescriber.
Alcohol and sedating medications
Loratadine itself is non-sedating, but combining it with alcohol or other CNS depressants may add sedative effects. Use caution when driving.
Use caution or avoid if
- Known hypersensitivity or allergy to loratadine or any component of the product
- Severe liver impairment — the dose interval may need to be extended; consult your prescriber
- Pregnancy and breastfeeding — loratadine passes into breast milk; discuss with your clinician before use
What most pages leave out
Availability
OTCLoratadine is available over the counter (OTC) in the United States as Claritin and as numerous generics at pharmacies, grocery stores, and online retailers — no prescription needed.
This covers more than one drug
The URL for this page pairs loratadine with omeprazole (Prevacid 24HR = lansoprazole). These are two entirely separate drugs with no therapeutic relationship. Loratadine is a non-sedating antihistamine for allergy symptoms. Omeprazole and lansoprazole are proton pump inhibitors (PPIs) that reduce stomach acid for acid reflux and heartburn — a completely different mechanism treating a completely different condition. If you are looking for information on Prevacid 24HR for acid reflux, that is outside the scope of this allergy-focused review. Please consult your pharmacist or prescriber for guidance on acid-reducing medications.
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
At the standard 10 mg dose, loratadine causes little to no drowsiness for most people — it is classified as a non-sedating second-generation antihistamine. A small number of users do report fatigue, so see how it affects you before driving. Increasing the dose above recommended amounts can raise the risk of side effects including sedation, and is not advised without prescriber guidance.
An automated system on a previous site paired these two unrelated drugs together, likely by associating their brand names without recognizing that they treat entirely different conditions. Loratadine (Claritin) is an antihistamine for allergies. Omeprazole and lansoprazole (Prevacid 24HR) are proton pump inhibitors for acid reflux and heartburn. They have nothing to do with each other medically. If you need guidance on acid reflux medication, speak with your pharmacist or doctor.
Yes. Loratadine is the generic (active ingredient) name, and Claritin is the original branded product made by Bayer. Many generic versions of loratadine are also sold at a lower cost and contain the same active ingredient at the same strength. The FDA requires generics to be bioequivalent, so switching between a branded and generic loratadine product is generally safe.
Loratadine typically begins to reduce allergy symptoms within one to three hours of the first dose, with the effect lasting 24 hours. Taking it consistently each day — rather than only when symptoms flare — tends to give better control. For seasonal allergies, some people start it a few days before their allergy season begins to build up steady-state coverage.
Antihistamines like loratadine manage symptoms while you take them but do not modify the underlying immune response. Allergy immunotherapy — a clinician-supervised program of graduated allergen exposure — is the treatment approach aimed at building longer-term tolerance. An allergist can assess whether immunotherapy is an appropriate option for your specific triggers.
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.