Posted 8/23/2014 8:30 AM (GMT -7)
The OTC medications should respond within hours. The shorter the acting, the quicker the response.
The 24 hour meds like Claritin, Zyrtec or Allegra take about 2 hours to reach efficacy. Benedryl, about 30 min, but it lasts 6 hours.
If you have no relief after 2 days,try something else.