class="Serp__item__snippet--34vQF">Both Claritin ® and ZYRTEC ® help treat common allergy symptoms . ZYRTEC ® starts working at hour 1 on the first day you take it while Claritin ® doesn’t start working until hour 3. 2 See more in the ZYRTEC ® and Claritin ® allergy medicine comparison chart...