How can a spell that exists inside the stomach be treated?

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.

Spells can be treated through Sharee‘ah Ruqyah, by reciting the Quran over the bewitched person. Recite the first chapter of the Quran (Al-Faatihah), the verse of Al-Kursi [Quran 2: 255], chapters 113 and114 and whatever else you can read from chapter 2. Also, recite the verses that talk about nullifying magic in the story of Moosa (Moses) [Quran 7: 117-120], [Quran 10: 80-82], [Quran 20: 69] and [Quran 2:102].

Vital methods to nullify magic include: much supplication and resorting to Allaah the Almighty, performing obligations and maintaining a complete state of purity, performing the morning and night Athkaar (mentioning of Allaah) and Athkaar after the obligatory prayers, and reading chapter 2 of the Quran in full or whatever you can read from it.

Allaah Knows best.