Fluorescent dyes, frequently referred to in the apparel industry as neon, daylight fluorescent, or luminescent dyes, are specialized organic compounds capable of absorbing high-energy, short-wavelength light (such as ultraviolet and blue light) and instantly re-emitting it as lower-energy, longer-visible wavelengths (like vivid greens, yellows, oranges, and pinks). This simultaneous reflection of standard visible light combined with the converted UV emission creates an intense, glowing color profile that appears unnaturally bright to the human eye.

These colorants are predominantly formulated as specialized disperse or acid dyes, making them highly effective when applied to synthetic polymers like polyester and nylon. They are widely utilized in high-visibility safety garments, athletic sportswear, and fashion accents. Due to their delicate molecular structures, fluorescent dyes possess inherently lower lightfastness compared to standard textile dyes, meaning they tend to fade more rapidly under prolonged direct sunlight exposure.