Foul odors can often be a sign of an infection, but just because you have a foul smell does not mean that the bacteria or fungus that are making the smell have actually invaded your body (which would be an infection). Some signs of an infection would include redness, swelling, and pain or tenderness. As an infection progresses, you might also start to develop a fever
and other, more wide spread symptoms. Given the dark, moist folds of your umbilical region, they are perfect places for both bacteria and fungi to grow unless they are cleaned carefully and regularly. Even so, those who are immunosuppressed, obese, or have other medical issues can be pre-disposed to developing infections in these sites. If you are worried that you might have an infection, you can clean the area gently with a mild skin soap, water, or even a diluted concentration of other skin cleansing anti-bacterial products. Be careful not to irritate the skin with cleaning. The most important thing with any skin infection (or concern for an infection) is to make sure that you visit with your family physician
about anything that is either getting worse or refuses to get better over a period of time.