Allergies for Singers?

I live in New Mexico and have been suffering from bad allergies for a few days. I went to the doctor because I wasn't sure if it was allergies or a cold, but he said it was because of allergies. He prescribed me Allegra allergy medicine and also cough medicine. I am a singer. I'm studying music education at a university, and I have to sing all the time. These allergies have greatly affected my singing. My voice is scratchy, and I can't hit all of the notes in my range. It's like my head voice doesn't exist. Do you think these pills will help clear me up and get my singing back to normal?

Thanks for your input.