Hi, Hay fever, also known as allergic rhinitis, is a condition that causes symptoms such as a runny nose and itching in the eyes, nose, and throat due to exposure to allergens such as pollen, dust mites, and pet dander. These allergens cause the immune system to release histamine, a chemical that causes inflammation and allergy symptoms. Antihistamines are the most common treatment for hay fever symptoms. Zyrtec, Clarinex, and Benadryl are all antihistamines that work by blocking the effects of histamine in the body. While Zyrtec and Clarinex are non-sedating and can be taken during the day, Benadryl is a sedating antihistamine and can cause drowsiness. It is generally safe to take a non-sedating antihistamine such as Zyrtec or Clarinex in the morning and a sedating antihistamine such as Benadryl at night if needed. However, it is important to check with your healthcare provider or pharmacist before taking any new medications or combinations of medications, especially if you have any medical conditions or are taking other medications. They can advise you on the appropriate dosages and potential side effects or interactions. Additionally, there may be other treatment options for hay fever that can be explored with the guidance of a healthcare provider. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Priyanka, General & Family Physician