Loratadine Side Effects: What to Know

Overview

Loratadine is one of the best-tolerated antihistamines available for allergy relief. It is classified as a non-sedating or minimally sedating antihistamine, and side effects are generally uncommon and mild when they occur. Understanding the potential side effects, their frequency, and when they warrant medical attention can help people use loratadine safely and know when to seek guidance from a healthcare provider.

This page provides detailed information about loratadine’s side effects, organized by frequency and severity, along with information about risk factors and when to seek medical care.

Common Side Effects

Side effects from loratadine occur less frequently compared to many other antihistamines, including first-generation antihistamines and even some second-generation antihistamines like cetirizine. When side effects do occur, they are typically mild.

Headache

Headache is the most commonly reported side effect of loratadine. It occurs in approximately 12% of people taking the medication, which is only slightly higher than placebo rates (11%).

The headaches are generally mild and often resolve on their own. It is not always clear whether headaches are related to the medication, the underlying allergy symptoms, sinus pressure, or other factors.

Fatigue

Some people report feeling tired or fatigued while taking loratadine, though this occurs less frequently than with many other antihistamines. Fatigue rates with loratadine are generally comparable to or only slightly higher than placebo rates.

Dry Mouth

Dry mouth is a common side effect of many antihistamines, including loratadine, though it tends to be milder than with first-generation antihistamines.

Managing dry mouth:

Sipping water throughout the day
Chewing sugar-free gum to stimulate saliva production
Using sugar-free lozenges
Avoiding caffeine and alcohol, which can worsen dryness

If dry mouth is severe or persistent, discussing it with a healthcare provider is advisable.

Drowsiness

While loratadine is classified as a non-sedating antihistamine, some drowsiness can occur. However, studies show that drowsiness rates with loratadine (approximately 2 to 8% of users) are comparable to placebo rates, meaning they may not be directly caused by the medication.

Loratadine is significantly less likely to cause drowsiness compared to first-generation antihistamines and is also less sedating than cetirizine, another commonly used second-generation antihistamine.

Less Common Side Effects

Some side effects occur less frequently but are still reported by people taking loratadine.

Dizziness

Dizziness may occur in some people taking loratadine, though it is uncommon. When it occurs, it is typically mild.

Nervousness or Restlessness

Some people, particularly children, experience nervousness, restlessness, or hyperactivity while taking loratadine. This paradoxical stimulant effect is uncommon but recognized, especially in pediatric populations.

Gastrointestinal Effects

Possible gastrointestinal side effects include:

Nausea
Stomach discomfort or abdominal pain
Diarrhea
Vomiting (less common)

These effects are generally mild when they occur and often resolve on their own.

Difficulty Sleeping

Although uncommon, some individuals report difficulty sleeping or insomnia while taking loratadine. This is an infrequent but recognized side effect.

Other Less Common Effects

Additional less common side effects may include:

Sore throat
Dry eyes
Nosebleed (epistaxis)
Increased appetite
Weight gain (rare)

Rare but Serious Side Effects

Serious side effects from loratadine are rare, but they require prompt medical attention when they occur.

Severe Allergic Reactions

Although loratadine is used to treat allergic symptoms, some people can have an allergic reaction to the medication itself.

Signs of a severe allergic reaction may include:

Rash, hives, or itching
Swelling of the face, lips, tongue, or throat
Difficulty breathing or swallowing
Tightness in the chest
Rapid heartbeat

These symptoms require emergency medical attention.

Cardiovascular Effects

Rare cardiac side effects have been reported with loratadine, though they are extremely uncommon.

Potential cardiac effects include:

Rapid heartbeat (tachycardia)
Palpitations
Irregular heartbeat
Chest pain

While these are rare, people with pre-existing heart conditions should inform their healthcare provider before using loratadine.

Liver Effects

Extremely rare cases of abnormal liver function have been reported in association with loratadine use. Signs of liver problems include jaundice (yellowing of the skin or eyes), dark urine, pale stools, or severe abdominal pain. These symptoms require medical evaluation.

Seizures

Extremely rare cases of seizures have been reported in association with loratadine use, though a direct causal relationship is not always clear. People with a history of seizures should discuss loratadine use with their healthcare provider.

Severe Dizziness or Fainting

While mild dizziness can occur, severe dizziness or fainting is rare and may indicate a more serious reaction requiring medical attention.

Risk Factors for Side Effects

Certain factors may increase the likelihood or severity of side effects from loratadine, though overall the medication is well-tolerated across most populations.

Children:

May be more prone to paradoxical reactions such as hyperactivity, nervousness, or restlessness
Generally tolerate loratadine well when appropriately dosed
Liquid formulations are commonly used for younger children

Elderly individuals:

Generally tolerate loratadine well due to its low sedation profile
May have slower elimination of the medication due to age-related decline in kidney or liver function
Reduced kidney or liver function may increase side effect risk

Kidney Function

People with reduced kidney function may eliminate loratadine more slowly, potentially leading to higher drug levels and increased risk of side effects. Dosage adjustments are typically recommended for people with significant kidney impairment.

Liver Function

Because loratadine is metabolized in the liver, people with liver disease may process the medication differently and may be at increased risk for side effects. Dosage adjustments may be necessary.

Concurrent Medications

Taking loratadine along with other medications that are metabolized by the same liver enzymes may affect loratadine levels in the body.

Medications that may interact include:

Ketoconazole (antifungal)
Erythromycin (antibiotic)
Cimetidine (acid reducer)

These interactions rarely cause significant problems but may increase loratadine levels.

Individual Sensitivity

Some people are simply more sensitive to the effects of medications, including loratadine. This individual variation is normal and unpredictable.

Comparing Side Effects with Other Antihistamines

Loratadine is notable for having one of the most favorable side effect profiles among antihistamines.

Compared to cetirizine:

Loratadine causes significantly less drowsiness (2-8% vs 10-14%)
Both have similar rates of headache and dry mouth
Both are well-tolerated overall

Compared to first-generation antihistamines (diphenhydramine):

Loratadine causes far less drowsiness
Loratadine has less anticholinergic effects (dry mouth, urinary retention, constipation)
Loratadine is generally better tolerated for daily long-term use

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

Long-Term Use Considerations

Loratadine is considered safe for long-term use in most people when taken as directed for chronic allergy management.

Tolerance and Effectiveness

Some people report that loratadine becomes less effective over time, though this is not a universal experience. If this occurs, consulting a healthcare provider about alternative options may be helpful.

No Significant Withdrawal Effects

Unlike some medications, loratadine does not typically cause withdrawal symptoms when stopped. However, allergy symptoms will return once the medication is no longer active in the body.

Regular Monitoring

People who take loratadine long-term, particularly those with kidney disease, liver disease, or other health conditions, may benefit from periodic check-ins with their healthcare provider to ensure the medication remains appropriate.

Interactions with Alcohol

Loratadine is less likely to interact with alcohol compared to first-generation antihistamines or even cetirizine. However, combining any antihistamine with alcohol is generally not recommended, as alcohol itself can cause drowsiness and impaired coordination.

While loratadine’s interaction with alcohol is minimal, caution is still advisable, particularly when driving or operating machinery.

Managing Minor Side Effects

For people who experience mild side effects but wish to continue using loratadine, several strategies may help:

For headache:

Ensure adequate hydration
Take the medication with food
Monitor whether headaches are related to the medication or underlying allergies
Consider over-the-counter pain relief if appropriate

For dry mouth:

Stay well-hydrated
Use sugar-free gum or lozenges
Consider a saliva substitute if needed

For mild fatigue:

Take the medication in the evening if timing flexibility exists
Ensure adequate sleep and hydration
Monitor whether fatigue improves with continued use

If side effects persist or worsen, consulting a healthcare provider is advisable.

Phenylketonuria Considerations

Some loratadine formulations, particularly orally disintegrating tablets and chewable tablets, contain phenylalanine, an amino acid that must be restricted in people with phenylketonuria (PKU).

People with PKU should carefully read product labels and choose formulations that do not contain phenylalanine, or consult with their healthcare provider about appropriate options.

When to Contact a Healthcare Provider

Medical guidance should be sought in certain situations related to side effects.

Contact a healthcare provider if:

Side effects persist or worsen over time
New or unusual symptoms develop after starting loratadine
There is uncertainty about whether a symptom is related to the medication
Side effects significantly interfere with daily activities
Questions arise about whether loratadine is still appropriate to use
Considering switching to a different antihistamine

When to Seek Emergency Care

Some symptoms require immediate medical attention.

Seek emergency medical care if:

Difficulty breathing, wheezing, or chest tightness occurs
Severe swelling of the face, lips, tongue, or throat develops
Signs of anaphylaxis appear (severe rash, rapid pulse, dizziness, severe difficulty breathing)
Irregular or rapid heartbeat occurs
Severe dizziness, fainting, or loss of consciousness occurs
Seizures occur
Signs of a severe allergic reaction develop

These symptoms may indicate serious adverse reactions or other medical emergencies requiring immediate evaluation.

Sources

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

U.S. Food and Drug Administration (FDA). Loratadine Label Information.
MedlinePlus, U.S. National Library of Medicine. Loratadine.
National Institutes of Health (NIH). Loratadine—Adverse Effects Profile.
American Academy of Allergy, Asthma & Immunology. Antihistamine Safety and Side Effects.
FDA Adverse Event Reporting System (FAERS). Loratadine Safety Data.
Clinical Reviews in Allergy & Immunology. Safety of Second-Generation Antihistamines.
Journal of Allergy and Clinical Immunology. Comparative Safety of Antihistamines.