What is the ruling on biting one's nails while fasting?

All perfect praise be to Allaah, the Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

Biting the nails does not break one's fast unless parts of the nails are swallowed deliberately. However, a Muslim should stop this act because it might harm one's health, as specialist doctors say.  It was authentically narrated on the authority of Ibn ‘Abbaas that the Prophet, sallallaahu ‘alayhi wa sallam, said: "[Let there be] no harm, nor the reciprocation of harm." [Ahmad and Ibn Maajah]

Allaah Knows best.