Does using a finger to apply antiseptic ointment to the anus after defecating invalidate the fast?

Scholars differ regarding the ruling on a fasting person inserting something into their anus. The majority of scholars hold that it invalidates the fast, citing as evidence that breaking the fast occurs when something enters the stomach.

Others, such as Ibn Hazm, Ibn Taymiyyah, and Ibn Uthaymeen, are of the view that it does not invalidate the fast, due to the absence of proof for invalidation, and because the default is the validity of the fast until evidence for its invalidation is presented.

If it is possible to delay the enema until after breaking the fast, that is more cautious. However, if that is difficult, the fast is not invalidated, according to the preponderant opinion.