Cetirizine vs. Loratadine: Which Antihistamine Fits Your Allergy Symptoms?

Cetirizine (Zyrtec) and loratadine (Claritin) are both second-generation antihistamines that can ease sneezing, runny nose, itchy eyes, and hives. Cetirizine may cause more drowsiness for some people, while loratadine is often described as less sedating. Neither is a good emergency treatment for a severe allergic reaction. This article compares cetirizine vs. loratadine by symptoms, side effects, safety cautions, and when to ask a clinician or pharmacist.

Cetirizine vs. loratadine: how they are alike

Cetirizine and loratadine belong to the same drug class: H1 antihistamines. Histamine is a chemical your body releases during an allergic response. It can contribute to sneezing, itching, watery eyes, a runny nose, and hives. These medicines block histamine at the H1 receptor, so they may reduce those symptoms.

Both are called second-generation antihistamines. Compared with older drugs such as diphenhydramine (Benadryl), they are generally designed to cause less sedation. Both are sold over the counter in the US in several forms, including tablets and liquids. Product forms and age ranges vary by brand, so the Drug Facts label on the package is the guide.

Both drugs have been studied for several conditions, including allergic rhinitis and hives. Wide study does not make any one of them the right choice for every person.

Differences that may matter to you

The table describes general patterns. People respond differently, and one drug can work well for a friend and poorly for you. If one does not help after you have used it as the label directs, a pharmacist or clinician can talk through alternatives.

Drowsiness and thinking clearly

Drowsiness is the difference people notice most. Product labels and clinical reviews generally describe cetirizine as somewhat more sedating than loratadine for some people, although both are considered less sedating than first-generation antihistamines. Check the Drug Facts label on your product for its drowsiness warning. Even though cetirizine is called "less sedating," a noticeable number of people still feel drowsy on it. Several factors contribute to how sleepy any one person feels, including their own body chemistry and other medicines or alcohol. Until you know how a new antihistamine affects you, be cautious about driving or operating machinery.

Which symptoms each one may help

For allergic rhinitis (hay fever), the International Consensus Statement on Allergy and Rhinology reviews oral antihistamines as a treatment option for sneezing, itching, and runny nose. Antihistamines often help less with nasal congestion. If a stuffy nose is your main problem, see our article on chronic nasal congestion, since other treatments or other causes may be involved.

For itching and hives, the PubMed Central review of chronic urticaria in adults describes H1 antihistamines as a common first-line approach, and a separate review of H1 antihistamines in skin disease discusses their role in itchy skin conditions. Our article on hives covers causes and emergencies in detail. Persistent hives or hives with other symptoms deserve a clinician's evaluation.

Choosing between them for your situation

If daytime sleepiness is a concern

If you drive, study, or work in a setting where alertness matters, loratadine is often considered first because it is described as less sedating. That is a general pattern, not a promise. Cetirizine is sometimes taken in the evening by people who notice drowsiness, but ask a pharmacist or your clinician about timing for your situation.

If symptoms need faster relief

Onset of relief can differ between products and people, so check the Drug Facts label and ask a pharmacist. Neither medicine is meant for instant relief of severe symptoms. If you are not sure whether what you are feeling is an allergy at all, MedlinePlus has overview pages on allergy, itching, and rashes that can help you describe symptoms to a clinician.

If one did not work

Trying the other drug is a reasonable conversation to have with a pharmacist. Do not take two different antihistamines at once unless a clinician tells you to; combining them may increase side effects such as sleepiness, particularly in older adults and children. Many cold and allergy combination products also contain an antihistamine, so check labels for duplicate ingredients. MedlinePlus has a page on cold and cough medicines that explains how combination products are labeled.

Side effects and cautions

Possible side effects of both medicines can include headache, dry mouth, and fatigue. Cetirizine is more likely to cause sleepiness for some people than loratadine. Avoid alcohol, sedatives, sleep aids, and other antihistamines, including diphenhydramine (Benadryl) found in some cold and nighttime products, unless a clinician or pharmacist says the combination is appropriate, because they may add to drowsiness and other side effects. Tell your pharmacist about everything you take, and avoid driving or operating machinery until you know how the medicine affects you.

Itching after stopping cetirizine

Newer cetirizine and levocetirizine labels warn that some people have developed severe itching (pruritus) after stopping the medicine, mostly after taking it daily for a long time. This appears to be uncommon. If you take cetirizine every day for months, ask your clinician or pharmacist how to approach stopping it. If intense itching starts after you stop, tell a clinician so they can evaluate it and discuss options. Check the current Drug Facts label on your product for this warning.

"-D" products and other combinations

Zyrtec-D and Claritin-D also contain pseudoephedrine, a decongestant. The Drug Facts label advises asking a clinician first if you have high blood pressure, heart disease, thyroid disease, diabetes, glaucoma, an enlarged prostate, or take an MAOI. Read the label on your product. These products are often kept behind the pharmacy counter in the US. Multi-symptom cold, flu, and nighttime products may also contain an antihistamine. Check the Drug Facts label and ask a pharmacist before choosing one.

Tell your clinician or pharmacist before using either medicine if you:

• Have kidney or liver disease, since your body may clear these drugs differently and the amount on the label may need adjusting.
• Are pregnant or breastfeeding: your clinician can weigh the options using current guidance for your situation.
• Are an older adult, who may be more sensitive to sedation. Ask a clinician or pharmacist whether the label amount suits you.
• Take other prescription medicines, sedatives, sleep aids, or other antihistamines that could interact, or drink alcohol regularly.
• Are giving the medicine to a child. Use the age range and amount on the product label, and ask a pediatrician or pharmacist, rather than estimating an amount yourself. For a child under 2, ask a clinician before giving either medicine.

Do not change how you take a prescribed allergy medicine without checking with the prescriber. Read the Drug Facts label on the package every time, since formulas and strengths differ between brands and store versions.

Antihistamines are not a treatment for anaphylaxis

Anaphylaxis is a severe, sudden allergic reaction that can involve the airway, breathing, circulation, or several body systems at once. The PubMed Central review of H1 antihistamines in anaphylaxis describes epinephrine as the first-line treatment, and 911 should be called. The same review discusses why antihistamines have a supporting role at most: they may ease itching and hives but do not reverse airway swelling or low blood pressure. Taking cetirizine or loratadine and waiting to see if a severe reaction improves can be dangerous.

Food allergy is a common trigger of severe reactions. If you or your child has a known food allergy, MedlinePlus has a food allergy overview, and your clinician can explain an emergency plan, including whether you should carry epinephrine.

When allergy medicine is not the answer

Not every sneeze, cough, or itch is an allergy. A cough that lingers can have many causes, including asthma, reflux, and infections, and an antihistamine may not address it. Our article on persistent cough covers what clinicians consider. If you have used an antihistamine as directed for the time the label allows and symptoms continue, or symptoms keep returning, a clinician can combine your history, examination, and testing to look for the cause. For ongoing nasal allergy symptoms, the International Consensus Statement on Allergy and Rhinology discusses intranasal corticosteroid sprays as a common first-line option, so ask a clinician whether one suits you, along with allergy testing.

Wheezing, shortness of breath, or trouble breathing during a possible allergic reaction is an emergency: use prescribed epinephrine if you have it and call 911. New wheezing or shortness of breath without a clear allergic trigger also needs urgent medical evaluation. Call 911 if it is severe, getting worse, or you cannot speak in full sentences. Fever, thick discolored nasal discharge with facial pain, or symptoms in only one nostril are not typical of simple hay fever and are worth raising with a clinician.

A practical way to decide

• Pick one product and read its Drug Facts label for the active ingredient, age range, and warnings.
• Note when you take it and how you feel over the next days, including sleepiness.
• If drowsiness bothers you, ask a pharmacist whether the other option or different timing may suit you.
• Keep a short list of your symptoms and triggers to share with a clinician if the medicine is not enough.

When to Seek Medical Care