Yes, Cetirizine can make you feel tired, sleepy, and weak.

Cetirizine is an anti-allergic medication, not a steroid. It relieves the symptoms of allergy. It is used to relieve runny nose, sneezing and redness, itching, and watering of the eyes caused by hay fever or seasonal allergies. It also relieves similar symptoms caused due to allergies to substances, such as dust mites, animal dander, and mold. It is also used to treat symptoms of hives, including itching and rash.

You will notice an improvement within an hour of taking Cetirizine. However, it may take a little longer to notice the full benefits.

Sometimes the doctor may advise you to take two different antihistamines together if you are being treated for a severe itchy rash. If you are taking Cetirizine during the daytime, your doctor may prescribe another antihistamine for the night which causes sleepiness, especially if the itch makes it difficult for you to sleep. Do not take two antihistamines together unless recommended by your doctor.

The duration for which the medicine needs to be taken depends on the problem being treated. If you are taking it for an insect bite, you may need it for a day or two. Similarly, if you are taking it to prevent symptoms of chronic allergic rhinitis (inflammation of the nose) or chronic urticaria, you may need to take Cetirizine for a longer time. Talk to your doctor if you are unsure about the duration of using Cetirizine.

Cetirizine is safe if used as prescribed by your doctor. Moreover, it is unlikely to harm you if you take it for a long time. But, it is best to take Cetirizine for only as long as you need it.