Each area of your body has colonies of healthy bacteria. Around your nose may be one type. Another on your chin. Another on your forehead. Scientist disagree on how many different types are on our skin. But most say there could be several hundred.
What we believe happens is constant use of ointments/spot treatments causes the decline of the good bacteria’s density. When they decline to a certain point they stop doing their job of protecting your skin against the constant onslaught of the bad bacteria (like the ones that cause acne). The bad ones are in the air and everywhere.
All this is theory of course! It is hard to prove. All we know is this: Following our directions seems to help a lot of people long term!