Claritin (loratadine) typically starts working within about 1 to 3 hours after taking a dose, with some studies showing symptom relief as early as 75 minutes (around 1 hour and 15 minutes)

. The peak effect usually occurs within 1 to 2 hours of ingestion, and the medication's effects can last for about 24 hours, which is why it is usually taken once daily

. Some sources note that symptom relief may begin sooner, around 10-20 minutes in some cases, but the average onset time is closer to 1 to 3 hours

. Claritin-D, which includes a decongestant, can start relieving nasal congestion symptoms in as little as 30 minutes

. It is also noted that Claritin, like other second-generation antihistamines, may take some time to build up to full effectiveness when taken regularly, sometimes up to a couple of weeks, although many people notice improvement within a few days

Summary:

• Onset of action: about 1 to 3 hours (some studies show ~75 minutes)

• Peak effect: 1 to 2 hours after dose

• Duration: up to 24 hours

• Claritin-D (with decongestant) may start working in 30 minutes for congestion relief

• Full buildup of effectiveness may take days to weeks with regular use

This makes Claritin a relatively fast-acting, long-lasting allergy medication suitable for daily use.