Putting medicine in the nose while fasting.
Putting medicine in the nose in the state of fasting invalidates the fast, because a pathway exists in the nose for something to reach the stomach; for this very reason, exaggerating in Istinshaq (snuffing water into the nose) while fasting has been prohibited, therefore, one should avoid putting medicine in the nose in the state of fasting. (Aham Masail/Vol:4/Page:95)