Food additives are essential to guarantee processed foods’ safety throughout its journey from workshops or factories to shops or catering establishment and eventually to consumers. As one of the commonly-used food additives, nitrites upon reaction with amines would generate highly toxic nitrosamines (e.g., N,N-diethylnitrosamine, DEN) as inadvertent byproducts resulted from food processing or preparation which are known to cause hepatotoxicity and even cancer. Hence detecting nitrosamine-induced acute liver injury accurately would be conducive to planning optimal treatment and avoid any further deterioration. Herein we design an activatable probe (BHC-Lut) that can release the drug luteolin for therapy and the chromophore (BHC-OH) for NIR-II fluorescence/optoacoustic imaging upon being triggered by hepatic biomarker hydrogen peroxide. In the probe BHC-Lut, benzoindolium heptamethine cyanine with NIR-II fluorescent emission is adopted as the chromophore scaffold, the incorporation of triethylene glycol into benzoindolium ensures sufficient water solubility and enhances biocompatibility of the probe, and luteolin is coupled onto the chromophore via boronate linkage that acts as both H2O2-responsive unit and the fluorescence quencher. The probe itself is weakly emissive. In the presence of H2O2, the boronate bond is cleaved, and the chromophore BHC-OH and the drug luteolin are released, which produces evident NIR-II fluorescent/optoacoustic signals for imaging and wields therapeutic effect respectively. The probe BHC-Lut has been used in DEN-induced hepatic injury model in mice, and the results evince BHC-Lut’s capability for in-situ biomarker-activatable detection and imaging of the acute liver injury site as well as in-situ biomarker-triggered drug release for therapy.