This is an interesting and unfortunate problem that needs more information before a physician would be able to tell you why it is occurring. The amount of odor that comes from the skin is a function of the oils that the body makes as well as the bacteria that thrive on those oils. As the food supply accumulates and the bacteria increase, the smells increase accordingly. An increase in either side of the that equation will lead to more smell.
There are some things that will lead to increased oil production, like physical activity (which causes sweating), hormone changes, external temperature, and even the part of the month it is (if you are a female). Any of these can affect the oil side. The bacterial type should be constant, and washing helps to remove or kill them regularly. If you are making so much oil that the bacteria are able to thrive and make your hair smell after just one day, then you should continue to wash your hair daily, or perhaps consider changing hair care products. If the problem continues, or you are having other symptoms, please speak with your primary care doctor
in person. Additionally, this could be a good comment to bring up during your annual physical