How long should it take for my claritin (loratadine) to work?

1-2 hours: Most medications take one to two hours to be absorbed into the blood stream. Some, such as steroids, need to be taken for several days to build up to their full effect, but this is not the case with antihistamines.

Up to 1 hour: Claritin (loratadine) can work relatively quickly in most people. That is, it usually works within 30 minutes. However, in some people it may take up to 60 minutes to have its full effect. If it is not working within that time, or if the duration of effect becomes less and less, seeing an allergy specialist for allergy testing would be recommended as other treatments may be more effective.

About 1.5 hours: Onset of clinical relief is about 1 hour for zyrtec and Allegra and about 1.5 hours for claritin (loratadine). To read the study, go to: http://www.Ncbi.Nlm.Nih.Gov/pubmed/15176489.