This is a difficult question to answer definitively and one that must be discussed with an allergist. The best theory I can give you for why this might occur involves your immune system and a signaling molecule called histamine. Histamine is a protein that immune cells use to communicate. It may sound familiar because histamine has become fairly well known in the lay community due to its role in allergies. A typical situation where histamine is released is in an allergic reaction to an allergen such as pollen. Pollen enters the nose and binds to receptors on certain cells in the immune system (such as mast cells). The binding of this allergen triggers a reaction where the immune cell releases histamine into the surrounding tissue. In the nose, histamine causes blood vessels to dilate and release fluid into the nasal mucosal tissue, causing a stuffy, runny nose. It also causes excitation of nerve endings which send signals to the brain that there is an irritation in the nose, causing sneezing. So why all this talk about allergies. Well, allergens are not the only thing that can cause immune cells to release histamine. Temperature changes can cause the release of histamine as well. A common example is hot water, which you may have noticed can cause your skin to get red and sometimes itchy. I suspect you may wash your face with warm water and this may be causing the release of histamine, leading to short term runny nose and sneezing after you wash your face. Another possibility is that there is an irritant in your facial soap or somewhere else in your bathroom that is causing an allergic reaction when you shower or wash your face. The only way to determine whether you have an allergy, such as one to a facial soap, is to visit an allergist and get allergy testing. It is very likely that the phenomenon you are experiencing is natural and not indicative of any problem. However, if you have an allergy to soap, fragrance, or even something in your bathroom like dust or mold, it may be beneficial for you to know what triggers the allergy, so that you can avoid the substance in the future. For that reason, you may want to visit an allergist so you can undergo testing and possibly treatment.