) It should be clear that according to the majority of Islamic jurists, administering medicine through the ears or putting oil in them while fasting invalidates the fast. However, according to the Shafi'i and Maliki schools of thought, fasting is only invalidated if the medicine reaches the brain or the throat. On the other hand, Hanafi jurists consider the fast invalidated because the medicine reaches the brain or throat.
This makes it evident that according to the Hanafi school of thought, the primary reason for the fast being invalidated is not due to a "Shariah nas" (i.e., the Holy Quran and the Sunnah) but simply because the medicine ends up reaching the brain or throat ultimately.
In religious matters such as this, where the jurists have unified upon the opinion of medical experts rather than a "Shariah nas", the perspective of medical experts cannot be ignored. Regarding this issue, all medical experts unanimously agree that there is a thin, strong membrane in the ear that prevents medicine from reaching the brain or throat unless the membrane tears or perforations occur, allowing the medicine to directly reach the throat.
Therefore, if the membrane of the ear is intact, putting medicine in the ear while fasting does not invalidate the fast.
However, it is better to avoid administering medicine through the ears while fasting, in accordance with the verdict of the majority of jurists, as this eliminates doubts.