Loratadine: Uses, Side Effects, Dosages, and Interactions

Published August 16th, 2021 by Erik Rivera
Fact Checked by
Chris Riley
Medically Reviewed:
Dr. Angel Rivera

Seasonal and perennial allergies affect millions of Americans each year, causing uncomfortable symptoms like nasal congestion, sneezing, itchy, watery eyes, and more. 

Individuals suffering from allergies may not always be able to avoid exposure to the allergens that cause their symptoms, but medications like loratadine can help treat and even prevent symptoms when taken regularly.

What is Loratadine?

Loratadine is a generic medication that is best known under the brand name Claritin. The medication belongs to a class of drugs called antihistamines, which are commonly used to treat symptoms associated with allergic reactions. 

Antihistamines work by preventing histamine, a natural chemical released by the body in response to an allergen, from binding to cells in the body and causing the symptoms associated with an allergic reaction. Histamines can cause itching, runny nose, watery eyes, itchy eyes, sneezing, hives, and just about any other miserable allergy symptom you can think of. 

There are two primary categories of antihistamines that are used to treat allergy symptoms: first-generation antihistamines and second-generation antihistamines. 

First-generation antihistamines include medications like diphenhydramine, the active ingredient in Benadryl, which work rapidly to relieve allergy symptoms but are commonly associated with side effects like significant drowsiness because they cross the blood-brain barrier. Loratadine is a second-generation antihistamine. 

Second-generation antihistamines are associated with far fewer side effects than first-generation antihistamines because they do not cross the blood-brain barrier. As a result, they are better suited for daily use in most people and can be used for the long-term treatment and prevention of allergy symptoms.

What is Loratadine Used To Treat?

Loratadine is a second-generation antihistamine that is used for the treatment of symptoms associated with some types of allergic reactions

Specifically, loratadine is used to treat symptoms associated with allergic rhinitis, or hay fever; these symptoms include itching, runny nose, watery eyes, and sneezing. Loratadine is also used to provide relief from itching caused by hives. 

Loratadine is not appropriate for the treatment or prevention of all kinds of allergic reactions, such as serious allergic reactions to food, medication, insect stings, or latex. Instead, loratadine is most effective when used to treat nasal symptoms associated with allergic rhinitis, which is a type of allergic reaction that occurs in response to environmental allergens on a seasonal or year-round (perennial) basis.

What Causes Allergic Rhinitis?

Allergic rhinitis, commonly referred to as hay fever, is a group of allergy symptoms that affect the nose and sinuses. Allergic rhinitis occurs in response to the presence of environmental allergens, which are substances that cause no problems for most people but cause a defensive immune reaction in people with allergies. 

Common triggers of allergic rhinitis include pollen from grass, trees, weeds, or flowers, indoor allergens, such as pet hair or dander, dust mites, and mold, or other irritants, including smoke, perfume, and vehicle exhaust. 

When the body detects the presence of an allergen, it begins to release inflammatory mediators, including histamines, which then bind to receptors on the surface of cells in the body. The histamine molecules then start to send chemical messages to the cells of the body, directing them to cause the uncomfortable allergy symptoms many people are familiar with, such as runny nose, sneezing, itchy/watery eyes, itchy nose or throat, nasal congestion, and sinus pressure.

How Does Loratadine Treat Allergic Rhinitis?

Second-generation antihistamines like loratadine work by binding to histamine receptors on the cells of the body to prevent histamine from attaching to the receptors. This prevents the release of the chemical messages that cause sneezing, itching, and increased mucus production. 

How Long Does It Take For Loratadine To Work?

Loratadine tends to work slower than diphenhydramine, a first-generation antihistamine that provides quick relief. In general, loratadine typically starts to relieve symptoms over the course of one to three hours and reaches its peak effect after about eight to twelve hours. 

Patients taking the 24-hour formula will experience relief for an entire day, while patients taking the 12-hour formula will need to take a second dose of the medication. 

When taken daily during periods of allergen exposure, loratadine can help control allergic rhinitis regularly.

What Are the Benefits of Using Loratadine?

Second-generation antihistamines like loratadine offer many benefits for allergy relief compared to first-generation antihistamines. Loratadine is less commonly associated with drowsiness and lethargy than first-generation antihistamines like diphenhydramine, which means it is safe for daily use in patients who have ongoing allergies. 

The medication is easily available for purchase over the counter and is highly affordable, especially when purchased in the generic form rather than the brand name Claritin. Additionally, the medication comes in a variety of different forms and has formulas designed especially for kids, which means that even people who have a hard time swallowing pills are likely to be able to use the medication to find relief from allergy symptoms. 

In general, loratadine is considered well-tolerated and the medication can be used safely on patients across a wide range of ages with appropriate medical supervision. The drug can be taken regularly or as needed and does not need to be taken with food.

How Do I Know What Dose of Loratadine To Take?

Loratadine is commonly sold in both a 12-hour formula and a 24-hour formula for both children and adults. The 12-hour formula typically contains 5 mg of loratadine and is intended to be taken twice per day. This formula comes in the form of a dissolvable tablet for adults and in the form of chewable tablets, reditabs, or liquid when manufactured for children. One dose of loratadine contains 5 mg in the children’s formula as well.

The 24-hour formula of loratadine is intended to be taken once a day. This formula contains 10 mg of loratadine and is available in the form of oral tablets, dissolvable tablets, liqui-gels, and chewables. Regardless of which form of the 24-hour medication you choose, the drug should be taken only once per day. The children’s 24-hour formula also contains 5 mg of loratadine.

Are There Any Side Effects I Should Be Aware Of?

The side effects associated with loratadine are consistent with the side effects caused by many other second-generation antihistamines. Although loratadine is less likely to cause side effects than first-generation antihistamines like diphenhydramine, it is still possible to experience side effects. 

Side effects commonly associated with loratadine include:

  • Headache
  • Dry mouth
  • Sore throat
  • Drowsiness
  • Fatigue
  • Nervousness
  • Sleepiness
  • Diarrhea
  • Eye redness
  • Hoarseness
  • Blurred vision
  • Feeling tired
  • Stomach pain
  • Nosebleed
  • Skin rash

Rare, but serious side effects associated with loratadine can include:

  • Allergic reactions
  • Rapid heart rate
  • Seizures 
  • Jaundice (yellowing of the skin or eyes)

Like all medications, loratadine can rarely cause allergic reactions in some individuals. Patients who experience any of the following signs of an allergic reaction should seek emergency medical attention: hives, difficulty breathing, or swelling of the face, lips, tongue, or throat.

Are There Any Drug Interactions Associated With Loratadine?

Loratadine is associated with relatively few drug interactions. However, patients should provide their doctor or pharmacist with a list of all prescription medications, over-the-counter drugs, dietary supplements, and herbs they are using in order to ensure that they do not experience any drug interactions that could be harmful. Loratadine may interact with certain kinds of antibiotics, some antifungal medications, and drugs used to reduce the amount of acid in the stomach (proton pump inhibitors). 


Loratadine, a generic medication commonly sold under the brand name Claritin, is a second-generation antihistamine that is commonly used to treat symptoms of allergic rhinitis (hay fever) or redness and itching caused by hives. 

Side effects associated with loratadine commonly include headache, nosebleed, mouth sores, nervousness, stomach pain, red or itchy eyes, dry mouth, sore throat, difficulty falling asleep or staying asleep, weakness, and diarrhea. 

Talk to your doctor about any medications you are using, including both prescriptions and over-the-counter drugs, as well as dietary supplements and herbs, in order to avoid a potentially harmful drug interaction.

References and Sources:

Loratadine | U.S. Library of Medicine 

Allergic rhinitis | U.S. Library of Medicine 

Diphenhydramine | U.S. Library of Medicine 

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