When you think about allergies, you probably think of a runny nose, itchy eyes, and sneezing, but they can also take a toll on your voice in several ways:
An allergic reaction can cause your vocal cords to swell.
Postnasal drip -- when mucus moves from your nose into your throat -- can irritate your vocal cords.
Coughing and clearing your throat can strain your vocal cords.
Antihistamine drugs for allergies can dry out mucus in your throat. This may harm your vocal cords, which need moisture to work.