Loratadine: Uses, How It Works, and Safety Information

Overview

Loratadine is a second-generation antihistamine commonly used to relieve symptoms of allergies. It is available over the counter in the United States under the brand name Claritin and as generic loratadine. The medication was approved by the FDA for prescription use in 1993 and became available for over-the-counter purchase in 2002.

Loratadine is classified as a second-generation antihistamine, which means it is less likely to cause drowsiness compared to older, first-generation antihistamines such as diphenhydramine or chlorpheniramine. Among second-generation antihistamines, loratadine is considered one of the least sedating options available.

This page provides an overview of loratadine, including what it is used for, how it works, common forms and strengths, who should use caution, and important safety considerations.

What Loratadine Is Used For

Loratadine is commonly used to manage symptoms associated with allergic conditions. These symptoms occur when the immune system reacts to substances such as pollen, dust mites, pet dander, or other allergens.

Common uses include relief of symptoms from:

Seasonal allergic rhinitis (hay fever)
Year-round (perennial) allergic rhinitis
Allergic conjunctivitis (itchy, watery eyes)
Hives (urticaria)
Itching from allergic skin reactions

Specific symptoms that loratadine may help relieve:

Sneezing
Runny or stuffy nose
Itchy nose, throat, or eyes
Watery eyes
Itching from hives or other allergic skin reactions

Loratadine treats the symptoms of allergies but does not address the underlying allergic condition or prevent allergic reactions from occurring. It works by blocking the effects of histamine, a chemical released during allergic reactions.

How Loratadine Works

Loratadine works by blocking histamine receptors in the body. Histamine is a chemical messenger released by the immune system when it encounters an allergen. When histamine binds to receptors on cells throughout the body, it triggers allergic symptoms such as itching, swelling, mucus production, and increased blood flow to affected areas.

By preventing histamine from binding to its receptors (specifically H1 receptors), loratadine reduces or prevents these allergic symptoms from developing. This mechanism is the same for all antihistamines, though different antihistamines have varying properties in terms of how long they last, how well they cross into the brain, and how likely they are to cause drowsiness.

Loratadine is considered a peripheral antihistamine, meaning it primarily acts outside the central nervous system. It crosses the blood-brain barrier minimally, which is why it is one of the least sedating antihistamines available. Studies show that drowsiness rates with loratadine are comparable to placebo.

The medication does not cure allergies or prevent future allergic reactions. It provides symptomatic relief while it is active in the body.

Available Forms and Strengths

Loratadine is available in several forms to accommodate different preferences and age groups.

Common forms include:

Tablets (standard and orally disintegrating)
Capsules (liquid-filled)
Chewable tablets
Oral solution (liquid)
Syrup

Common strengths available over the counter:

10 mg tablets (standard adult dose)
5 mg chewable tablets (typically for children)
1 mg per mL oral solution (typically used for children)

Some products combine loratadine with a decongestant (such as pseudoephedrine) for additional relief of nasal congestion. These combination products have different indications and safety considerations compared to loratadine alone.

For detailed information about dosing, see our page on loratadine dosage.

Who Should Use Caution or Avoid Loratadine

While loratadine is generally considered safe for most people when used as directed, certain individuals should use caution or discuss use with a healthcare provider before taking it.

People who should use caution include those with:

Kidney disease or reduced kidney function (loratadine is eliminated primarily through the kidneys)
Liver disease (loratadine is metabolized in the liver)
Phenylketonuria (some formulations contain phenylalanine)
Pregnancy or breastfeeding

Special considerations:

Loratadine is metabolized in the liver to an active metabolite called desloratadine (which is also available as a separate medication). People with severe liver disease may need dosage adjustments.

People with phenylketonuria should check product labels, as some orally disintegrating tablets and chewable formulations contain phenylalanine, an amino acid that must be restricted in this condition.

Side Effects Overview

Most people tolerate loratadine very well, and it is considered one of the least sedating antihistamines available. Side effects are generally uncommon and mild when they occur.

Common side effects may include:

Headache
Fatigue
Dry mouth
Drowsiness (uncommon, occurring at rates similar to placebo)

Less common side effects may include:

Dizziness
Nervousness or restlessness (more common in children)
Stomach discomfort
Nausea

Serious side effects are rare but may include:

Severe allergic reactions (rash, itching, swelling, difficulty breathing)
Rapid or irregular heartbeat
Severe dizziness or fainting

For comprehensive information about side effects, their frequency, and when to seek medical attention, see our detailed page on loratadine side effects.

Drug Interactions and Combination Products

Loratadine has relatively few significant drug interactions compared to older antihistamines. However, some interactions are worth noting.

Potential interactions include:

Medications that inhibit liver enzymes (such as ketoconazole, erythromycin, cimetidine) may increase loratadine levels in the body
Alcohol may have additive effects, though loratadine is less likely than other antihistamines to interact with alcohol
Other antihistamines may have additive effects

Important considerations for combination products:

Many over-the-counter allergy and cold medications contain multiple active ingredients. Taking loratadine along with other products that also contain antihistamines can result in excessive dosing. Always check the labels of all medications to avoid unintentional duplication of active ingredients.

People taking prescription medications should inform their healthcare provider before adding loratadine to ensure there are no concerns with their specific medication regimen.

Onset and Duration of Action

Loratadine has a moderate onset of action compared to some other antihistamines.

Timing characteristics:

Typically begins to work within 1 to 3 hours after taking it
Peak effects occur at approximately 1 to 2 hours (for the active metabolite, peak occurs at 3 to 4 hours)
Effects last approximately 24 hours
Taken once daily for ongoing allergy management

While loratadine takes longer to begin working compared to cetirizine (which typically starts working in 20 to 60 minutes), both medications provide effective 24-hour symptom control with once-daily dosing.

For detailed information about how long loratadine takes to work and factors that influence its effectiveness, see our page on how long loratadine takes to work.

Special Populations

Children

Loratadine is available for children ages 2 and older in appropriate formulations and doses. Liquid forms and chewable tablets are commonly used for younger children. Product labels provide specific guidance based on age and weight.

Elderly Individuals

Older adults generally tolerate loratadine well due to its low sedation profile. However, those with reduced kidney or liver function may require dosage adjustments.

Pregnancy and Breastfeeding

Loratadine is classified as Pregnancy Category B by the FDA, meaning animal studies have not shown risk, but there are no adequate studies in pregnant women. Many healthcare providers consider it a reasonable option for managing allergies during pregnancy, but medical guidance should be sought.

Loratadine passes into breast milk in small amounts. While it is generally considered compatible with breastfeeding, discussing use with a healthcare provider is advisable.

People with Kidney or Liver Disease

Because loratadine is metabolized in the liver and eliminated through the kidneys, people with reduced function in either organ may need dosage adjustments. Healthcare provider guidance is important for these populations.

Loratadine vs Other Antihistamines

Loratadine is one of several second-generation antihistamines available over the counter. Key distinguishing features include:

Compared to cetirizine:

Loratadine is less sedating (drowsiness rates similar to placebo)
Loratadine has a slower onset of action (1 to 3 hours vs 20 to 60 minutes)
Both provide 24-hour symptom control
Both are generally safe and effective

Compared to first-generation antihistamines (diphenhydramine):

Loratadine is much less sedating
Loratadine lasts longer (24 hours vs 4 to 6 hours)
Loratadine is taken once daily vs every 4 to 6 hours

For a detailed comparison, see our cetirizine vs loratadine comparison page.

When to Seek Medical Care

While loratadine is generally safe when used as directed, certain situations warrant medical attention.

Contact a healthcare provider if:

Allergy symptoms do not improve after several days of regular use
Symptoms worsen or new symptoms develop
Unusual or concerning side effects occur
There is uncertainty about whether loratadine is appropriate for a specific situation
Allergy symptoms significantly interfere with daily activities despite medication use

Seek emergency medical care if:

Difficulty breathing or wheezing occurs
Severe swelling of the face, lips, tongue, or throat develops
Signs of a severe allergic reaction appear (hives, severe rash, rapid pulse)
Chest pain, rapid heartbeat, or severe dizziness occurs
Fainting or loss of consciousness occurs

These symptoms may indicate a serious condition requiring immediate medical attention and are not necessarily related to loratadine use but may occur in the context of severe allergic reactions or other medical emergencies.

Sources

This information is based on data from the following authoritative sources:

U.S. Food and Drug Administration (FDA). Drug Approval Package: Loratadine.
MedlinePlus, U.S. National Library of Medicine. Loratadine.
National Institutes of Health (NIH). Loratadine—Clinical Pharmacology.
American Academy of Allergy, Asthma & Immunology. Antihistamine Use in Allergic Disease.
FDA Consumer Health Information. Safe Use of Over-the-Counter Antihistamines.
Clinical Pharmacology and Therapeutics. Second-Generation Antihistamines: Efficacy and Safety.