Optical brighteners, optical brightening agents (OBAs), fluorescent brightening agents (FBAs), or fluorescent whitening agents (FWAs), are chemical compounds that absorb light in the ultraviolet and violet region (usually 340-370 nm) of the electromagnetic spectrum, and re-emit light in the blue region (typically 420-470 nm) by fluorescence. These additives are often used to enhance the appearance of color of fabric and paper, causing a "whitening" effect; they make intrinsically yellow/orange materials look less so, by compensating the deficit in blue and purple light reflected by the material, with the blue and purple optical emission of the fluorophore. The most common classes of compounds with this property are the stilbenes, e.g., 4,4′-diamino-2,2′-stilbenedisulfonic acid. Older, non-commercial fluorescent compounds include umbelliferone, which absorbs in the UV portion of the spectrum and re-emit it in the blue portion of the visible spectrum. A white surface treated with an optical brightener can emit more visible light than that which shines on it, making it appear brighter. The blue light emitted by the brightener compensates for the diminishing blue of the treated material and changes the hue away from yellow or brown and toward white.

For the human body: (1) No irritation to skin: After years of animal and human tests, it has been shown that even if the skin directly contacts the pure CBS fluorescent whitening agent, it is not irritating to the skin and will not cause skin allergies. Optical brighteners are not absorbed by the skin. Even if the optical brightener CBS may adhere to the skin in a small amount during use, it will not react with human skin, and it is easy to be completely washed off through daily washing activities (such as hand washing, bathing, etc.) and will not be washed by the skin absorb. Therefore, direct skin contact with CBS-added laundry detergent will not cause harm; (2) No adverse effect on wound healing: The article "Toxicological Properties of Fluorescent Whitening Agents" published in "German Dermatology" in 1994 pointed out that even direct contact of optical brightener for textiles with wounds did not adversely affect wound healing or cause pathological changes in human skin; (3) Metabolism: For the fluorescent whitening agent CBS, it can be quickly and completely excreted through normal metabolism. Metabolic studies in mice show that after a large dose of optical brightener for detergents is fed, most of the whitening agent will be quickly excreted through the intestinal tract and will not be absorbed by the intestinal tract. No fluorescent whitening agent remains in its blood, liver, kidney, brain, muscle and fat, that is, it will not cause accumulation in the body. Therefore, even if a small amount of fluorescent whitening agent CBS enters the human body in daily life, it will be quickly excreted through the normal metabolic process; (4) The fluorescent whitening agent CBS has no teratogenicity and no carcinogenicity. Acute toxicity studies on a variety of animals and chronic toxicology experiments in mice for up to two years have proved that CBS is a non-toxic substance, non-teratogenic, non-carcinogenic, and non-mutagenic.

For the environment: (1) CBS has high degradability, and its usage in detergents is not high. After rinsing and dilution and one general treatment of domestic sewage, CBS can be reduced by more than 95%, and the final amount entering the environment is very small. Even if a small amount of water enters surface water (such as rivers), it will undergo photodegradation very quickly, and the products of photodegradation can easily undergo secondary degradation, that is, they are eaten by microorganisms and then decomposed into carbon dioxide and other substances that have no impact on the environment; (2) No effect on the biological chain
CBS fluorescent whitening agent will not stay in biological tissues and organs after being ingested by fish. Laboratory studies have shown that even after fish have been exposed to high concentrations of CBS for a period of time, CBS will not accumulate in the fish for two days. Based on the results of long-term ecological studies, CBS is not harmful to the environment.

Masterbatch (MB) is a solid additive for plastic used for coloring plastics (color masterbatch) or imparting other properties to plastics (additive masterbatch). A liquid dosage form is called liquid color. Masterbatch is a concentrated mixture of pigments and/or additives encapsulated during a heat process into a carrier resin which is then cooled and cut into a granular shape. Masterbatch allows the processor to color raw polymer economically during the plastics process. The alternatives to using masterbatches are buying a fully compounded material (which may be more expensive and less open to e.g. color variability of the product), or compounding from raw materials on site (which is prone to issues with achieving full dispersion of the colorants and additives, and prone to preparing more material than what is used for the production run). In comparison with pure pigments, masterbatches require more storage space and their lead times are longer. Another disadvantage is additional exposure of heat ("heat history") to both the carrier and the additive; this may be important e.g. for marginally thermally stable pigments. As masterbatches are already premixed compositions, their use alleviates the issues with the additive or colorant clumping or insufficient dispersion. The concentration of the additive in the masterbatch is much higher than in the end-use polymer, but the additive is already properly dispersed in the host resin. In a way their use is similar to uses of ferroalloys for adding alloying elements to steels.