Voldemort’s lack of a nose is a well-known visual motif in the Harry Potter films, and there isn’t a single canonical in-universe line that gives a definitive, explicit medical explanation. The most widely accepted answers come from the combination of J.K. Rowling’s books and the film adaptations, along with fan and publisher discussions. Core explanation

• In-universe progression: Voldemort gradually becomes more monstrous and inhuman as he splits his soul into Horcruxes and pursues increasingly dark magic. This transformation is often cited as the underlying cause of his altered appearance, including the loss or deformation of his nose. The process of turning toward extreme dark magic is described in the books as stripping away humanity in various ways, which fans and commentators interpret as contributing to his facial changes over time. This view is reinforced by scenes and descriptions surrounding his rebirth in the graveyard and his revived, snake-like visage.

Alternative theories you’ll see in discussions

• Horcrux-linked degradation: Each Horcrux adds a fragment of soul while eroding the creator’s humanity; some argue this correlates with changes to his facial features, including the nose. While not stated as a medical fact in the text, it’s a common interpretive lens used to explain his evolving appearance across the franchise.

• Nagini venom or post-resurrection effects: Some analyses connect his post-resurrection appearance to Nagini’s venom or other magical effects at the graveyard, suggesting that magical interventions changed his physiology. This is a speculative reading rather than a canonical medical cause, but it appears in fan discussions and secondary analyses.

Note on the films’ depiction

• Visual design: The filmmakers intentionally presented Voldemort as bald, pale, and noseless to emphasize his serpentine and inhuman nature, aligning with descriptions of him as a “snake-like” villain. The look was created through makeup and prosthetics to reinforce the character’s loss of humanity, rather than as a direct, explicit medical consequence spelled out in dialogue.

Bottom line

• The absence of a nose is best understood as a cinematic and literary symbol of Voldemort’s total immersion in dark magic and his gradual loss of humanity through Horcrux creation and ritualistic power, rather than a single explicit medical event described in the text.

If you’d like, I can pull exact passages from the books or provide a concise, scene-by-scene timeline of how Voldemort’s appearance evolves across the series to anchor these interpretations.