Owned by McNEIL-PPC, Inc, Zyrtec is an oral antihistamine designed to provide fast allergy relief for symptoms such as sneezing, runny nose, sore throat, and itchy watery eyes. Brussels, Belgium-based company UCB, which was founded by Emmanuel Janssen in 1928, developed Zyrtec in... Read More the 1980s. UCB originally focused on producing industrial chemicals before working in the pharmaceutical field, and now offers products that aid in allergy relief, respiratory disease, and central nervous conditions such as epilepsy and Parkinson’s disease. Zyrtec fights against indoor and outdoor triggers such as dust, mold, pet dander, pollen, and grass to relieve allergies for up to 24 hours at a time. Zyrtec comes in a number of forms including tablets, liquid gels, and D tablets that also boast congestion relief, and start working within one hour. Zyrtec 10mg 24 Hour Allergy Tablets are designed for adults and children 6 years and older to relieve indoor and outdoor allergies for a 24-hour period and start working after just one hour. Its compact size makes keeping a box handy in a purse or backpack a cinch.