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You mentioned that you have the fever. You can use Paracetamol. You can take it up to three times a day and can stop if your temperature comes down.
Now, coming to Cetirizine, it is used for allergy, cold, etc. If you are having a flu type of fever, that is, fever with the cold or itchy throat, then yes you can use it along with the Paracetamol.
I suggest you take both the medicines together. You can use Levocetirizine, which avoids sleepiness. Hence, you can be focused in your work. Consult your specialist doctor, discuss with him or her and take medicine with their consent.
For further queries consult a general practitioner online --> https://icliniq.com./ask-a-doctor-online/general-practitioner