Quality of Skin Care Products and their Ingredients

Joel L. Zatz, PhD, Professor of Pharmaceutics, Rutgers College of Pharmacy, Piscataway, NJ

One of the results of increasing life expectancy is the need to care for an ever-growing number of elderly people, many of whom are not completely ambulatory. This requires skilled nursing care and the assistance of products that help "normalize" various bodily functions and processes. A large group of these products is used on the skin to augment this organ's natural protective functions and help return the skin to a healthy state when it has been compromised.

Several ingredients used in skin care products have been criticized as being excessively harsh, allergenic, or otherwise unsuitable for use, especially in the elderly population. Preservatives, in particular, have been condemned, leading to a proliferation of "preservative-free" products. Other descriptive/promotional phrases with negative connotations are "fragrance-free" and "emulsifier-free." The use of these designations might suggest that preservatives, fragrances, emulsifiers, and a number of other ingredients serve no important function, are superfluous in terms of product quality, and, therefore, should be left out of all skin care products. While this is obviously not the case, neither is the obverse. Ingredients should be carefully chosen to support or maintain the overall effectiveness and utility of the product. If a preservative is needed, it should be there. If not required, it should be omitted. Thus, the ingredients in a skin care product should not represent a "laundry list" of substances chosen without purpose; each component should contribute to product performance.

Aspects of Product Quality

The quality of a dermatological product depends on a number of attributes. The four major requirements are stability, therapeutic activity, skin compatibility, and patient acceptability.

Stability--Stability is defined as a lack of significant change in properties over time. Chemical stability defines the persistence over time of various product components, especially the active ingredient(s). Good chemical stability also implies a lack of microbial growth during storage and use.

Content of the active ingredient is verified by a chemical assay specific for that compound, if one is available. In the absence of a reliable chemical assay, a biological assay may be used. Uniformity of drug content is also important, and pharmaceutical manufacturers usually assay samples from large batches before packaging, and from individual tubes, bottles, or jars after they are filled, to make sure that drug content is uniform throughout the batch.

Therapeutic activity--Products intended for use on the skin differ from most other drug products in the way that the base, or vehicle, functions. The vehicle, as the name implies, is supposed to deliver the drug to a locale (as on the skin) where it can either act or be absorbed for action at a remote location.

Skin compatibility--Ease of application and removal are two important characteristics of skin compatibility. A very important aspect of good skin compatibility is an absence of irritation and allergic response.

Patient acceptability--Patients (and caregivers) do not wish to use topical products that are unpleasant (greasy, smelly, or staining) or that spoil their appearance.

Product testing--A variety of chemical, physical, and biological tests help define product characteristics during development and after manufacture. Cell culture and other models have been used to assess the potential for irritation and cell damage.

A variety of factors must be considered in evaluating product quality. The building blocks of a product are its ingredients, which may be combined in many different ways. The function of several key ingredients, other than actives, as well as their limitations, should be reviewed, for example:

– Surfactants--function and irritancy

– Perservatives--commonly used perservatives, functions, effectiveness, concentration and perservative toxicity.

– Fragrances--functionality and
fragrance toxicity.

– Humectants--functionality and humectant toxicity.

– Emollients--functionality and elmollient toxicity.

Conclusion

The skin is a magnificent, durable organ that retains its protective function over many years. The stratum corneum's resistance to permeation endures almost from cradle to grave, although the repair rate after trauma is severely reduced in older individuals. Maintaining stratum corneum integrity is important, as damage to this thin, outermost skin layer can allow entry of deleterious substances and initiate a series of consequential problems. A variety of therapeutic and cosmetic skin care products are available to aid in this enterprise. The goal of the medical professional, patient, and/or caregiver is to choose products that will do the most good without simultaneously causing harm.

Although ingredients are its bricks and mortar, a product is not simply the sum of its parts. The effectiveness of a topical dermatological is influenced not only by the active ingredient and its concentration, but also by its form, the extent of occlusion by the vehicle, and the presence of certain pharmacologically inert formulation components.

When judging a product, consider the formulation as a whole, rather than focusing on ingredients as separate entities. Experience can be a useful guide to product performance and the potential for untoward reactions. Before selecting a product, consult the manufacturer for information on the length of time a product has been on the market and the incidence of skin reactions that have been reported. For new products, request safety testing information (such as dermal irritancy and sensitization) from the manufacturer.

Allergic reactions are very much an individual issue. A product that works well for more than 90% of the population may cause a reaction in a particular person. Patients should be queried about known allergies and shielded from exposure to products with problem components. When a reaction occurs, recognize that one of the active ingredients may be the cause or that the preservative or one of the other supportive ingredients may be the offending substance. Try to find a similar product that uses another active ingredient and another preservative. Giving the skin a short breather, allowing it to return to normal before making the switch, may be an alternative. Very often, simply removing the offending product will do the most good.

Optimizing quality requires a balancing act on the part of the manufacturer in order to utilize effective ingredients to support critical product functions while minimizing the possibility of skin reactions. Product development is something of an art, as well as a science. Caregivers can help by providing feedback on their experience to help manufacturers evaluate how well their products are doing and where improvement is necessary.

Excerpted with permission from Ostomy/ Wound Management. The quality of skin care products and their ingredients. Ostomy/Wound Management 2001;47(2):22–33 * * *