désensibiliser

"To desensitize" — a common medical and psychological term: reducing an allergic reaction through gradual exposure (désensibiliser un patient au pollen) or, figuratively, making someone less emotionally reactive to something (désensibiliser à la violence).

• Le traitement vise à désensibiliser les patients allergiques aux acariens. — The treatment aims to desensitize patients allergic to dust mites.
• Certains craignent que les jeux vidéo ne désensibilisent les jeunes à la violence. — Some fear that video games desensitize young people to violence.
• Cette thérapie désensibilise progressivement la peur des araignées. — This therapy gradually desensitizes the fear of spiders.

Used both medically (allergies) and psychologically (emotional numbing to violence or trauma) — context determines which sense applies; don't assume it always means the medical allergy treatment.