How long until clairtin 24 hour kicks in?

1 hr: You should know if it is helping an hour after taking it. It may even kick in before that. It can also depend on how good your body is at absorbing it and how fast it processes it out of your system.

Claritin (loratadine) = Placebo: I believe Claritin was shown to be no better than placebo. Zyrtec or Allegra might work better. Benadryl (diphenhydramine) is more likely to make you drowsy, but works great if you take it at bedtime.

Depends: According to the package insert, the onset of action of Loratadine (Clairitin) is 1-2 hours as is the onset of action of pseudoephedrine, the other ingredient. That being said, I know from personal experience and the experience of other patients, that it can take several days for congestion symptoms to truly resolve with the drug, depending on how much nasal inflamation you have. Hope this helps!

Usually: takes a few hours: however if you have severe allergy symptoms it may take several days to notice a significant improvement.

1-2 hrs: It will take 1-2 hrs to kick it but it is not a potent an antihistamine as Allegra (fexofenadine) or Zyrtec.