Hello. Thank you for asking at HCM. If you have not had any chronic allergy problem like allergic rhinitis, I would agree that oxygen is a possibility. Sometimes oxygen works as irritant for nasal mucosa and this irritation causes immediate sneezing and running nose. Mostly it is self-limiting. There is nothing serious in that. You need not to worry at all. If you have an allergic condition like allergic rhinitis in past, there are many possible allergens in a hospital environment like latex, drugs, etc. In that case taking medications like levocetirizine & montelukast helps. Hope this will be helpful to you. Wish you best of the health. Regards.