Is Zyrtec non-drowsy?

Zyrtec (cetirizine HCl) is an over-the-counter oral antihistamine used to treat itchy skin, hives, runny nose, sneezing, itchy eyes, and other year-round or seasonal allergy symptoms caused by allergens such as grass, dust mites, pollen, and pet dander. It is classified as an H1-antihistamine, a second-generation antihistamine, or a nonsedating antihistamine.

Although called nonsedating, Zyrtec can cause drowsiness in some people. Clinical studies report that about 14% of adults and 4% of children experience sleepiness while taking Zyrtec. In adults, the incidence of drowsiness tends to decrease each week as the body adjusts. If Zyrtec makes you drowsy, consider taking it at night or switching to another allergy medication.

Do other antihistamines cause drowsiness?

First-generation antihistamines (e.g., Benadryl, hydroxyzine) cross the blood–brain barrier and cause sedation because histamine in the brain helps keep you awake. Second-generation antihistamines (e.g., Allegra, Zyrtec, Claritin) cross minimally and are less likely to cause drowsiness. Research suggests Allegra is the least sedating of the second generation, and Claritin and Allegra are less likely to cause drowsiness than Zyrtec.

Why do some antihistamines make you drowsy?

• Examples: chlorpheniramine, diphenhydramine, meclizine, dimenhydrinate, hydroxyzine, doxylamine
• They cross the blood–brain barrier, causing sedation and are used as sleep aids or in cold/flu products.
• Side effects: increased fall risk in older adults, impaired driving, dry mouth, urinary retention, constipation.

Side effects of Zyrtec

• Nausea
• Vomiting
• Diarrhea
• Drowsiness
• Headache
• Sweating
• Numbness/tingling
• Altered taste
• Constipation
• Dry mouth
• Sore throat

Rare serious effects: difficulty urinating; allergic reactions with rash, swelling, dizziness, or breathing trouble.

What is Zyrtec‑D used for?

Zyrtec‑D contains cetirizine plus pseudoephedrine (a decongestant). It relieves allergy symptoms plus nasal congestion. Avoid pseudoephedrine products if you have high blood pressure, heart disease, or hyperthyroidism.

Takeaway

If OTC allergy medications don’t relieve your symptoms, consult a doctor or pharmacist. If one medication works well, continue it. If not, consider seeing an allergist for personalized treatment.

Sources

• Hong D et al. Efficacy of different oral H1 antihistamine treatments on allergic rhinitis: systematic review and network meta-analysis. Braz J Otorhinolaryngol. 2023;89(4):101272. Accessed Apr 9, 2025.
• Mann RD et al. Sedation with “non-sedating” antihistamines: Four prescription-event monitoring studies. BMJ. 2000. Accessed Apr 9, 2025.
• Zyrtec. Zyrtec Professional. Accessed Apr 9, 2025.