Sunset Yellow (E110) is an azoic dye synthetized from aromatic hydrocarbons, which is used to improve the physical–chemical properties of food products and their conservation; its chemical formula is C₁₆H₁₀N₂Na₂O₇S₂. Here, in order to characterize this azoic dye in powder and solution form, five spectral techniques were employed: Fourier Transform Infrared (FTIR), UV–Vis, Raman, Laser fluorescence and Terahertz (THz) spectroscopy. The Sunset Yellow’s morphology, structure and its chemical composition were studied by scanning electron microscopy (SEM), X-ray diffraction and energy-dispersive X-ray spectroscopy (EDXS). The thermal behaviour of Sunset Yellow was studied in correlation with its physical (refractive index, electric susceptivity, optical anisotropy) and chemical (acidity) properties. Thermal analysis effectuated in air indicates the evaporation of absorbed and physically bonded water up to 188 °C, after which the material possesses thermal stability up to 330 °C. The oxidative decomposition takes place in four exothermic steps of which the strongest between 510 and 643 °C develops a heat of 4519.6 J g⁻¹; at 913 °C, a residue of 31.77% is obtained. The study of optical properties of Sunset Yellow shows that the refractive indexes are decreasing when the temperature of the solution increases. The optical anisotropy of Sunset Yellow was studied under polarized light at room temperature. Sunset Yellow exhibits the phenomenon of birefringence on resulted crystallites by drying and crystallization at RT from aqueous solutions with concentrations of 1% and 5%. THz spectroscopy identified the THz spectral “signature” of Sunset Yellow at a few wavelengths. Sunset Yellow has biophysical properties when interacting with proteins (bovine serum albumin (BSA) and collagen). The biological properties of Sunset Yellow were observed through its antioxidant activity and phytotoxicity; while the antioxidant activity is proportional with increasing its concentration, the phytotoxicity study indicates that the Sunset Yellow does not present wheat (Triticum aestivum) growth phytotoxicity at low concentrations (when treating with aqueous solutions of 0.01–0.05%, it could increase its resistance to drought conditions), but at concentrations of 0.25% or higher, there are negative changes in wheat growth.