Metzitza

This question is extensively discussed in halachic literature, mainly in connection with the question of oral cleansing of the mila (metzitza) , the suspension of Shabbar due to mortal danger , and the laws of family purity

the rabbi who taught that one can omit metzitza is not fit to have any question of Jewish law brought before him, unless or until he retracts his words

Breast feeding during the post-partum period can transmit HIV indicating that oral or gastrointestinal mucosa may be a portal of entry for the virus. This has halachic implications for a Mohel who has to do metzitza. A variety of unusual transmissions have been reported.

Many rabbis contend that metzitza is a procedure mandated by the Gemara as a critical step in ensuring the cleanliness and promoting the healing of the incision. For that reason the Gemara insisted that it be performed even on Shabbat (as pikuach nefesh), and instructed that any mohel who neglected this step was to be removed from his position. page 123: Perhaps we have to conclude, then, that the violent opposition to any modification of metzitza procedure in the nineteenth century arose not from the particulars of the suggested changes but rather from an awareness that the entire controversy was fundamentally a ruse by the enemies of Judaism to destroy the foundation of Torah observance. Thus, they were resisted absolutely, on ideological rather than on technical grounds.

The Gemara (Shabbat 133b) regards Metzitza as a medical necessity and the Chochmat Adam (149:14) believes that our sages required Metzitza for health reasons. However the Avnei Nezer in his Teshuvot on Yoreh Deah (338) insists that Metzitza is an integral component of Brit Milah and is not done merely for health reasons. According to the Avnei Nezer, the significance of Metzitza is deeply rooted in Kabala.