For your allergies, an over-the-counter daily antihistamine like cetirizine or loratadine can help reduce symptoms, including post-nasal drip which often causes a sore throat. To directly soothe your throat, you can gargle with warm salt water, use throat lozenges, or take mild pain relievers like acetaminophen or ibuprofen. Stay well-hydrated with warm fluids. If your sore throat worsens, is accompanied by a high fever, or doesn't improve after a few days, please consult a doctor to rule out any bacterial infections.