No. If you are using commercially available sterile or distilled water for a nasal wash, you do not need to boil it before use, as it is already safe for this purpose. Ready-made saline solutions (sodium chloride nasal solutions) are also available and are generally the safest and most convenient option for nasal irrigation. If you are using tap water instead, it should be boiled for 3 to 5 minutes (or according to local public health guidance) and then allowed to cool to a lukewarm temperature before use. Always use clean equipment and prepare the nasal rinse as directed. If you are unsure about the type of water, the correct technique, or any specific medical need, consult your doctor or pharmacist before use.