Ointments and oils applied to the skin, pain-relief patches affixed to the body, and similar external applications may be absorbed in minute quantities through the skin and enter the bloodstream via capillaries. However, such absorption does not constitute nourishment nor does it resemble acts of eating and drinking undertaken for the purpose of sustaining the body.
Therefore, since these applications neither serve the function of nutrition nor fall within the legal category of consumption (akl wa shurb), they do not invalidate the fast.