Asthma & allergy
Antihistamine
Cetirizine
Also known as: Zyrtec
Best time
Evening
- 19:00–22:00
Evening dosing covers the early-morning peak in hay fever symptoms and sleeps off any drowsiness.
Moderate evidence
Supported by studies and drug pharmacology, but guidance varies between sources.
Why this time works
Histamine-driven allergy symptoms (sneezing, runny nose) are typically worst on waking. Taking cetirizine the evening before means peak protection by morning, and any mild sedation happens at night.
Body rhythm involved
Allergic rhinitis symptoms peak in the early morning.