<s>[INST] I had a dental procedure yesterday with nitrous-oxide used.  I have never had the gas before. A few hours after the procedure it seems I started developing a head cold with dull headache. I woke up this morning with the same. Is this a coincidence or is it possible? [/INST] Hi..Welcome to HEALTHCARE MAGIC..I have gone through your query and can understand your concerns..As per your complain it seems that you have side effects of the nitrous oxide gas leading to headache and cold like symptoms while it can also be due to viral infection that might have co-incidentally occurred with nitrous oxide inhalation..Nothing to worry as the symptoms will resolve soon in case if it is due to nitrous oxide anaesthesia it will gradually improve as the side effect of gas will wean off from the body..In case if it is due to cold then taking supportive treatment like decongestant nasal sprays, steam inhalation and using a humidifier in your room will help..Oral intake of decongestant like Phyenylephrine, mucolytics like ambroxol and along with it antihistamine like levocetrizine can help..Hope this information helps..Thanks and regards.Dr.Honey Nandwani Arora. </s>