Allowable ingredients and maximum allowable concentrations.
Sunscreen ingredients can be classified by the portion of UV radiation that they effectively absorb or block.
Chemical sunscreens that absorb Ultraviolet B (290-320nm)
Padimate O (290nm – 315nm)
Para-aminobenzoic acid (PABA) was one of the first chemical sunscreens to be widely available in the USA, but its association with a number of adverse reactions limited its use. PABA requires an alcohol vehicle when use in sunscreen commercial products. It may stain clothing, and it has been associated with a number of adverse reactions, including allergic and photoallergic contact dermatitis. Ester derivatives, mainly padimate O (octyl dimethyl PABA) and padimate A (amyl dimethyl PABA), became more popular, with greater compatibility in a variety of cosmetic vehicles and a lower incidence of adverse reactions. Padimate O is the most potent UV-B absorber. Because of problems with PABA formulations and reports of photoallergic reactions, both PABA and its ester derivatives have now been almost completely removed from sunscreen manufacturing. The decline in its use, along with the demand for higher SPF products, has led to the incorporation of multiple active ingredients into a single sunscreen product to achieve the desired SPF, replacing single PABA esters.
Octinoxate Octyl Methoxycinnamate (290nm – 320nm)
The cinnamates have largely replaced PABA derivatives as the next most potent UV-B absorbers. Octinoxate (OMC) is the most frequently used sunscreen ingredient.
Octisalate Octyl salicylate (280nm – 320nm)
Octisalate is used to augment the UV-B protection in a sunscreen. Salicylates are weak UV-B absorbers, and they are generally used in combination with other UV filters. Other salicylates must be used in higher concentrations. They all have a good safety profile.
Octocrylene (290nm – 320nm)
Octocrylene may be used in combination with other UV absorbers to achieve higher SPF formulas. Octocrylene used in combination with other sunscreen ingredients, such as avobenzone, may increase its overall stability in a specific formula.
Ensulizole Phenylbenzimidazole sulfonic acid (290nm – 320nm)
A sunscreen agent, formerly known as phenylbenzimidazole sulfonic acid. Ensulizole is the new established name that must be used on sunscreen labels. It is primarily a selective UV-B filter providing only minimal UV-A protection (weak protection up to 340nm). Most chemical sunscreen ingredients are oils that are soluble in the oil phase of emulsion systems, accounting, in part, for the heavy, greasy aesthetics of many of these products. Ensulizole is water soluble, and is often used in products formulated to feel lighter and less oily, such as daily use cosmetic moisturizers.
Chemical sunscreens that absorb Ultraviolet A (UV-AII 320-340nm, UV-AI 340-400nm)
Oxybenzone (270nm – 350nm)
Although benzophenones are primarily UV-B absorbers, Oxybenzone (benzophenone-3) absorbs well through UV-AII, with its primary activity between 290nm – 340nm; it extends the coverage beyond the UV-B range and into the UV-A range. It significantly augments UV-B protection when used in a given formula.
Methyl Anthranilate (Meradimate) (300nm – 320nm) 260-380
Anthranilates are weak UV-B filters, and they absorb mainly in the near UV-A portion of the spectrum. Anthranilates are less effective in this range than benzophenones, and are therefore not used as frequently.
Sulisobenzone (290nm – 320nm) water soluble
extend the coverage beyond the UV-B range and into the UV-A range, helping to make sunscreens broad-spectrum.
Avobenzone [Parsol 1789®] (300nm – 375nm)
Often referred to by its trade name, Parsol 1789®, avobenzone (butyl methoxydibenzoylmethane) provides superior protection through a large portion of the UV-A range, including UV-AI. Widely used in Europe for the last decade, the FDA approved avobenzone for use in the US in 1992. Potentially a significant addition to sunscreen products for true broad-spectrum UV protection, concerns have been raised regarding its photostability and its potential to degrade other sunscreen ingredients in products in which it is used. After about five hours of UV-A exposure, which equates to about 50 joules of energy, avobenzone imparts little photoprotective qualities to the sunscreen. Octocrylene and Mexoryl have been shown to stabilize avobenzone, to provide a long-lasting, stable and high level of UV-A protection.
Ecamsule [Mexoryl-SX] (320nm – 350nm )
Ecamsule (terephthalylidene dicamphor sulfonic acid) is more commonly known as Mexoryl? SX. It has been available in Europe and Canada for years and was approved in the United States in July 2006. Ecamsule provides protection within the UV-AII range (320-340nm; maximum absorption at 344nm), but is water soluble.
Mineral-based sunscreens that block Ultraviolet A (UV-AII 320-340nm, UV-AI 340-400nm)
Mineral-based sunscreens are inorganic chemical physical blockers that work by reflecting and/or scattering UV radiation. Titanium dioxide and zinc oxide function in this fashion. Poor cosmetic acceptance initially limited the widespread use of these ingredients until recently, when micronized forms have become available.
Titanium dioxide (290nm – 360nm)
Titanium dioxide can be classified as a broad-spectrum agent, which provides protection from both UV-B and UV-A radiation. However, pure titanium oxide is thick, pasty, and white, and often impractical for those who lead active lifestyles because it is not cosmetically appealing. By decreasing the particle size of this pigment to ultra fine or micronized grades (T-Cote®), thereby making it less visible on the skin surface, some of these advantages could be used. Products containing titanium dioxide still tend to whiten the skin secondary to pigment residue; adding other pigments that simulate flesh tones may partially camouflage this effect. The net effect may be that the user is inclined to use less of the product (a light application), effectively lowering the SPF. Hybrid products that use a combination of chemical UV absorbers and inorganic particulate sunscreens may represent a practical compromise. Titanium dioxide offers better UV-B protection than zinc oxide, which excels in the UV-A range.
Zinc oxide (290nm – 385nm)
Having been used for many years in opaque blocks, zinc oxide has been approved by the FDA as an allowable active ingredient in sunscreen products. The ideal sunscreen agent would be chemically inert, safe, and absorb or reflect through the full UV spectrum. Zinc oxide is one of the only truly broad-spectrum sunscreen ingredients that offers protection from both UV-B and UV-A radiation. Only zinc oxide blocks UV-B, UV-AII, and UV-AI rays, protecting uniformly from 290-380nm. No other sunscreen ingredient provides broader protection! Pure zinc-oxide preparations are the gold standard for sunscreen protection. However, pure zinc oxide is thick, pasty, and white, and often impractical for those who lead active lifestyles because it is not cosmetically appealing. But that has changed. Now the beneficial effects of zinc oxide are available in Z-Cote HP1?, a patented formulation of transparent micronized zinc oxide, coated with dimethicone. This is an elegant preparation of zinc oxide that enables the product to be utilized under make-up or over the entire body. Z-Cote? is the most advanced sun protection product available. In additon, zinc oxide is safe and gentle enough to be used on compromised or environmentally damaged skin. Zinc oxide is less whitening in this form than titanium dioxide and provides better UV-AI protection.
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