If you've been taking Zyrtec or Xyzal for your worsening allergy symptoms, there's a new side effect you should know about.

Some patients may suffer from unbearable itching across their entire body after stopping common allergy medications, health officials said. People who quit Zyrtec or Xyzal after using them daily for several weeks or longer have reported a rare but serious reaction known as pruritus.

Spring allergy season is in full swing, but the U.S. Food and Drug Administration has issued a warning about a rare but serious “severe itching” side effect from popular allergy medications that has affected hundreds of people.