Claritin (loratadine) is an antihistamine that blocks your body’s allergic response to pollen, dust, pet dander, and other triggers. It’s FDA-approved for two specific uses: relieving the nasal and non-nasal symptoms of seasonal allergies, and treating chronic hives of unknown cause. It works once a day, rarely causes drowsiness, and is available over the counter for adults and children 2 years and older.
How Claritin Works in Your Body
When you encounter an allergen like pollen or pet dander, your immune system releases a chemical called histamine. Histamine latches onto receptors in your nose, eyes, throat, and skin, triggering the familiar cascade of sneezing, itching, runny nose, and watery eyes. Claritin works by sitting on those same receptors first, preventing histamine from binding and setting off that chain reaction.
What sets Claritin apart from older antihistamines like Benadryl (diphenhydramine) is that it largely stays out of the brain. Older antihistamines cross freely into brain tissue, which is why they make you sleepy. Claritin is a second-generation antihistamine designed to work primarily in the rest of the body. In a large review of roughly 55,000 patients, only about 1% reported drowsiness while taking it, a rate virtually identical to placebo.
What Symptoms It Treats
Claritin targets both nasal and non-nasal allergy symptoms. On the nasal side, that means sneezing, a runny nose, and congestion. Non-nasal symptoms include itchy, watery eyes and an itchy throat or palate. If your main complaint is stuffiness, keep in mind that antihistamines are generally better at stopping a runny nose and sneezing than they are at clearing congestion. Some Claritin products add pseudoephedrine (sold as Claritin-D) specifically to address that.
The other approved use is chronic idiopathic urticaria, which is the medical term for ongoing hives that appear without a clear cause. Claritin reduces the itching, redness, and size of hive outbreaks by blocking the histamine that drives them.
How to Take It
The standard adult dose is 10 mg once a day, whether you use a tablet, chewable tablet, liquid-filled capsule, or orally disintegrating tablet. Children 6 and older take the same 10 mg dose. Children ages 2 to 5 typically take 5 mg once daily, usually as a liquid syrup (one teaspoonful). It is not recommended for children under 2.
You can take Claritin with or without food. One study found that eating a meal increased the amount of loratadine absorbed into the bloodstream by as much as 50 to 75%, but the resulting levels were still well below those shown to be safe in clinical trials using much higher doses. In practical terms, food does not meaningfully change how well the drug works or how safe it is.
Most people notice relief within 1 to 3 hours of taking a dose, and a single tablet covers a full 24-hour period. Taking it at the same time each day helps maintain consistent levels in your system. If you’re using it for seasonal allergies, starting before peak pollen season can help you stay ahead of symptoms rather than chasing them.
Side Effects
Claritin is one of the best-tolerated allergy medications available. The most commonly reported side effects in clinical trials were headache, dry mouth, fatigue, and drowsiness, but all of these occurred at rates very close to what patients taking a sugar pill experienced. Drowsiness specifically affected only about 1% of people taking the standard 10 mg dose.
That said, combining Claritin with other sedating substances can tip the balance. Taking it alongside Benadryl, certain cough suppressants, opioid pain medications, or benzodiazepines may increase the risk of feeling drowsy or sluggish. Alcohol can have a similar additive effect.
Who Should Be Cautious
If you have significant liver or kidney problems, your body clears loratadine more slowly. In those cases, the recommended approach is to take 10 mg every other day instead of daily, giving your body extra time to process each dose. The drug’s half-life increases as liver function declines, so this adjustment prevents the medication from building up to unnecessarily high levels.
People with a history of heart rhythm problems should use Claritin carefully. While it’s far safer for the heart than some older antihistamines, there is a small potential for it to affect heart rhythm, particularly when combined with certain other medications. One notable interaction involves the heart medication amiodarone, which taken alongside Claritin may increase the risk of a dangerous rhythm disturbance.
Claritin is processed in the liver by two specific enzyme pathways. Certain medications, including some antifungals and antibiotics like erythromycin and clarithromycin, slow down those pathways and can raise loratadine levels in your blood. Grapefruit juice does the same thing. This does not mean you can never combine them, but it is worth being aware of if you’re taking multiple medications.
Some formulations, particularly the orally disintegrating tablets, contain phenylalanine. This is only a concern for people with phenylketonuria (PKU), a rare inherited condition, but it is worth checking the label if that applies to you.
Claritin vs. Other Antihistamines
The three most popular second-generation antihistamines are Claritin (loratadine), Zyrtec (cetirizine), and Allegra (fexofenadine). All three work by blocking histamine receptors and all are available over the counter. The differences are subtle but can matter depending on your priorities.
Zyrtec is often considered slightly more potent for severe allergy symptoms, but it causes drowsiness in about 14% of users, a much higher rate than Claritin’s 1%. Allegra is comparable to Claritin in terms of low sedation but may wear off a bit faster for some people. Claritin sits in a comfortable middle ground: effective for mild to moderate allergies with the lowest drowsiness profile of the three. If you’ve tried one and it isn’t controlling your symptoms well enough, switching to another is a reasonable next step since people respond differently to each one.