Hello. It is completely understandable to feel concerned about these new symptoms. Both Xyzal and Levosiz contain the exact same active generic medication, levocetirizine. Because they are chemically identical, switching between them is highly unlikely to directly cause your new cough or snoring. These symptoms might instead suggest that your underlying allergy is acting up, or you may have a mild, unrelated respiratory irritation. Since breathing changes can affect your sleep and comfort, I warmly encourage you to speak with your doctor to have your throat and chest evaluated. We want to ensure you get the right relief and rest easy.