Is there anything I can get from the grocery store or drug store for my urticaria until I can see a doctor?

Antihistamines. Once-daily antihistamines such as zyrtec, Allegra or Claritin (loratadine) (ini that order) often work well for hives. Sometimes you might need to take one in the morning, and another one at night. If the hives don't go away with two antihistamines per day, see your doctor.
Urticaria treatment. Urticaria, or hives, is often an acute reaction from a variety of triggers, including insect bites, food reactions, viral infections, animals, dust and chemicals, and medications. Aside from the rash, the itching is usually the most severe problem. Antihistamines, such as benadryl, (diphenhydramine) claritin, zyrtec and allegra, can be helpful to control the itching, Claritin and Allegra being less sedating.