This page is for educational purposes only. Always consult a doctor or pharmacist before taking any medicine, especially if you have kidney disease, are pregnant, or are giving cetirizine to a child. For persistent or severe allergic symptoms, consult a doctor rather than relying on over-the-counter antihistamines alone.
Cetirizine is a second-generation antihistamine used to relieve allergy symptoms such as runny nose, sneezing, itchy eyes, and hives. It is one of the most commonly used allergy medicines in Korea.
Cetirizine is a second-generation antihistamine that works by selectively blocking H1 histamine receptors. Histamine is a chemical released by immune cells in response to allergens (such as pollen, dust, animal dander, or certain foods), causing the familiar symptoms of allergic reactions — itching, sneezing, watery eyes, runny nose, and skin reactions. By blocking histamine receptors, cetirizine significantly reduces these symptoms.
Compared to first-generation antihistamines (such as chlorphenamine/Piriton), cetirizine is less sedating because it crosses the blood-brain barrier less readily. However, some people do experience drowsiness, so caution is advised when driving or operating machinery. In Korea, cetirizine is sold under brand names including Zyrtec and Reactine and is available over the counter at pharmacies.
Cetirizine is effective for seasonal and perennial allergic rhinitis (hay fever), allergic conjunctivitis, chronic urticaria (hives), and insect bite reactions. Korea's seasonal spring pollen and recurring fine dust days mean allergic rhinitis is very common among residents, making cetirizine one of the country's most frequently used medications. It is typically taken once daily and provides relief for up to 24 hours.
While generally safe, cetirizine should be used with caution in patients with kidney impairment (dose adjustment may be needed), and should be avoided with alcohol. It is considered safe for children over 2 years when using appropriate paediatric dosing formulations.
Key Points
- Second-generation antihistamine — less sedating than older antihistamines
- Relieves runny nose, sneezing, itchy eyes, hives, and allergic skin reactions
- Once-daily dosing; available OTC in Korea as Zyrtec, Reactine
- May cause drowsiness in some people — caution when driving
- Avoid combining with alcohol — increases sedation risk
- Dose adjustment required in kidney impairment
Causes & Risk Factors
- Seasonal allergic rhinitis (hay fever) — pollen, grass, and tree allergies
- Perennial allergic rhinitis — dust mites, pet dander, mould
- Allergic conjunctivitis — itchy, watery, red eyes
- Chronic urticaria (persistent hives) and acute allergic skin reactions
- Insect bite and sting reactions causing local or urticarial reactions
- Food allergy-related urticaria (not for severe systemic reactions — use epinephrine)
When to See a Doctor
- If allergy symptoms persist despite antihistamine use — allergy testing and specialist referral may be needed
- If you experience a severe allergic reaction (anaphylaxis): throat swelling, difficulty breathing, severe drop in blood pressure — call 119 immediately
- If you have kidney disease — dose adjustment may be needed
- If you are pregnant or breastfeeding — consult your doctor before use
- For children under 2 years — paediatric dosing must be guided by a doctor
- If you are taking CNS depressants (sedatives, sleeping pills) — additive sedation risk
For emergencies in Korea, call 119
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This content is published for educational purposes only. For accurate diagnosis and personalised treatment, consult a licensed KMA physician in Korea.
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Medical Disclaimer
This article is published by DoctorsInKorea.com for educational and informational purposes only. It does not replace a professional clinical evaluation by a licensed healthcare provider. For accurate medical diagnosis and personalised treatment paths, please book an appointment with a licensed KMA physician. For immediate life-threatening medical emergencies in Korea, please call 119.
Sources & References
Last reviewed: May 29, 2026