Sunscreens And Sunscreen Testing

Authored by: Dr. Kim Baughman, Microbac Laboratories, Inc.

Because of the increased understanding of the effects of UV radiation from the sun on skin health, the use of sunscreens has become the norm for many of us when we know we are going to be exposed to the sun for an extended period of time. Regulation of these products is the responsibility of the FDA and current labeling includes the Sun Protection Factor (SPF), as well as a list of the ingredients in the product. A product with an SPF of 10 indicates that it would take a person wearing the sunscreen 10 times as long to develop sunburn as it would without sunscreen. However, UV light is broken down into UVA and UVB components. The tests used to determine SPF values of sunscreens only determine the effectiveness of blocking UVB rays because this light is primarily responsible for sunburns. However, UVA light penetrates the skin deeper and also contributes to long-term skin damage.

The FDA has recently proposed a new labeling system that will also include a rating of one to four stars, indicating the product's effectiveness against UVA light. Thus, all products would have an SPF rating, indicating its effectiveness against UVB rays, and a separate rating for effectiveness against UVA rays. As this change is still only a proposal, it is not certain if or when this will take effect. Implementation has already been delayed.

Sunscreen ingredients are regulated and are broken down into two groups: organic ingredients that tend to absorb UV light; and inorganic ingredients, which reflect UV light. As part of the QC testing by sunscreen manufacturers, the levels of the various sunscreen ingredients are tested on each batch of product. The organic chemicals are generally tested by high-performance liquid chromatography (HPLC), or gas chromatography (GC), while the inorganic ingredients are tested by titration or, more commonly, by atomic spectroscopy methods such as inductively-coupled plasma spectroscopy.

The FDA-approved active sunscreen product ingredients are listed below:

Organic Ingredients
Aminobenzoic acid (PABA) up to 15 percent
Avobenzone up to 3 percent
Cinoxate (2-Ethoxyethyl p-methoxycinnamate) up to 3 percent
Dioxybenzone up to 3 percent
Ecamsule (terephthalylidene dicamphor sulfonic acid)
Homosalate up to 15 percent
Menthyl anthranilate up to 5 percent
Octocrylene up to 10 percent
Octyl methoxycinnamate (octinoxate) up to 7.5 percent
Octyl salicylate up to 5 percent
Oxybenzone up to 6 percent
Padimate O up to 8 percent
Phenylbenzimidazole sulfonic acid up to 4 percent
Sulisobenzone up to 10 percent
Trolamine salicylate up to 12 percent

Inorganic Ingredients
Titanium dioxide up to 25 percent
Zinc oxide up to 25 percent

Because the inorganic ingredients zinc oxide and titanium dioxide reflect radiation, they provide protection from all components of UV light. However, one of the issues with these ingredients is their opaqueness - they leave an unattractive whitecolored film on the skin. New technology has been developed that can eliminate this disadvantage. The processing of the zinc oxide and titanium dioxide into nanoparticles allows formulation of a product that is transparent, yet reflects all components of UV radiation. Analytical laboratory testing of these products is the same as for products using larger particles.

Microbiology Testing

Another facet of sunscreen quality control is testing for bacteria, yeast and mold, and pathogens, including: S. aureus, Salmonella, E Coli, P. Aeruginosa, Clostridia, and C. albicans. USP methods, the same as for pharmaceutical products, are used to test the raw materials and/or the finished product for microbial contamination.

Products

In addition to being added to traditional "sunscreens", UV blocking ingredients are added to face powders, lip balms, moisturizers, foundations, make-up bases, hand creams, and other cosmetic products. This industry continues to expand.

Microbac Laboratories Inc. is a full service FDA-inspected cGMP laboratory. We perform the full range of sunscreen chemical assay and microbiological tests discussed above.

SOURCE: Microbac Laboratories Inc.