How quickly do antihistamines work?
Most antihistamines start working within 30 minutes to an hour after you take them. The speed depends on the type of antihistamine and how you take it—tablets work more slowly than nasal sprays or eye drops, which can take effect within minutes. Peak effectiveness usually happens around 1-2 hours after taking a tablet.
Key points:
- Tablet antihistamines typically begin relieving symptoms within 30 minutes, with full effect by 1-2 hours
- Nasal sprays work faster (15-30 minutes) but only treat nose symptoms, while eye drops work within minutes but only treat eye symptoms
- Newer second-generation antihistamines like cetirizine work faster than older first-generation types
- Most antihistamines provide relief for 12-24 hours, though some older types last only 4-8 hours
This text has been fact-checked for accuracy by medino's clinical team.