Why Skin Care Products Work Sometimes, But Not Others


Everyone has experienced the unexplained difference in efficacy of skin care products from client to client. Why is it that a cosmeceutical works so well on one client for reducing wrinkles, redness and pore size, but does not work at all for another? The answer is bioavailability.


Bioavailability in skin care products is the ability for the active ingredient to perform its function at the site intended in the skin for optimal effect. Several well-known factors contribute to active ingredient bioavailability. These can be easily remembered by The Three D’s: Dose, Delivery and Depth.

Dose. How much active ingredient is in the product? Is it dose-dependent, which means it can be too little—most common, or too much—which can cause side effects? What is the optimal dose?

Depth. Is the active ingredient achieving the proper depth in the skin to make a difference? Will a lightening active ingredient reach the epidermal-dermal junction to affect the melanocytes? Will a collagen-producing peptide reach the papillary dermis to effect a fibroblast cell to produce collagen? If the active ingredient stays on the surface of the skin or penetrates too deeply, the product will be ineffective if the intended target cells are at a different depth.

Delivery. How does an active ingredient get to its intended cellular target? Does it need to be in liposomal form? Nanoparticle? Oil-in-water emulsion? Water-in-oil emulsion? Microemulsion? Hydroalcoholic? The base in which the active ingredient is in is critical to bioavailability.


Often times, a film is left on the upper layers of the skin—this can also hinder the product’s efficacy. The potential for residue, or product occlusion, to be present on skin that interferes with the bioavailability of active ingredients is just one consideration to take into account that is relative to the ability for a skin care cosmeceutical to work well.

Several key types of product residue directly affect the performance of skin care active ingredients. They are, in order of most-to-least common: fatty alcohols that deposit from cleansers; makeup; sunscreen; and salicylic acid.

Fatty alcohols from cleansers. Cleansers fall into three basic formulation categories: foaming cleansers—gels and liquid; cleansing creams—milks, lotions and cold creams; and scrubs—which incorporate abrasive particles to exfoliate.

Foaming cleansers are usually nonocclusive, meaning they generally do not leave residue on the skin that inhibits active ingredients from penetrating and becoming bioavailable.

Cleansing creams and scrubs generally leave some type of occlusion from ingredients, such as cetyl alcohol or cetearyl alcohol. In cleansers, these ingredients are designed to deposit on the skin while washing to provide a moisturizing and smoothing effect.

When skin is thoroughly clean, it is squeaky clean like a rubber surface. If skin feels soft and smooth after washing, then something has deposited on it and can potentially occlude skin and reduce the bioavailability of active ingredients. Image 1 shows a client who had their skin cleansed in a clinic in preparation for an acne clinical study. Her skin presents with randomly spaced papules and pustules covering most of her face. Image 2 is a specialized color ultraviolet image, which detects different types of occlusions. Even after a professional cleanse, significant occlusion is evident on this client’s face. With randomized distribution of noncystic lesions, it is often an occlusion that covers the entire face as a result of the occlusive ingredients of creamy-type cleansers. Bacterial colonies have started to form under the occlusions as well, indicated by bright florescent spots, which further stresses the skin.

Active ingredient bioavailability is affected with this type of occlusion; subsequently, acne medication is not as effective as it could be. Anti-aging active ingredients, anti-inflammatory ingredients and skin lighteners also would have reduced bioavailability.

If using imaging equipment is not an option, check the product itself. A rule of thumb is that if the cleanser is transparent when held up to a light source, then occlusive ingredients are probably not in the product. If the product is opaque or pearlescent, then it is likely occlusive agents are present in the product. When providing clients with a regimen, include a clear, foaming cleanser, as this will help to remove occlusions over time and allow the bioavailability of the active ingredients to increase with prolonged use.

Makeup. Makeup often acts as a barrier to optimal bioavailability of active ingredients. There are many variables to skin occlusion when it comes to different formulations of makeup: pigment load—which is the concentration of all the pigments combined in the formula; binders—which are present in loose powder and pressed powder; and, most importantly, the particle size of the pigment.

Some makeup can have the tendency to make pores more accentuated or enhance imperfections in skin. Some types of makeup do not have optimal particle size distribution, so the pigment settles into pores and defects in skin, making the overall surface appear to have uneven tone and texture. What is not visible is that these makeup types also tend to adhere to skin and may not come off completely, even though it is not obvious to the naked eye.

Image 3 is the skin of a client who looks to have no makeup on. However, Image 4 of the same client under color ultraviolet imaging reveals that there is makeup or occlusion on the skin across her nose, cheeks and chin, as indicated by the reddish-brown diffuse areas across mid-face. Once again, the bioavailability of active ingredients in skin care products is affected greatly due to the occlusion that may not always be evident.

Sunscreens. A large part of good skin health is the application of a broad-spectrum sunscreen each day with reapplications as directed. The importance of promoting proper skin health and protection cannot be over-emphasized.

There are physical and organic sunscreen ingredients. The physical sunscreen ingredients are generally a variety of titanium dioxide and zinc oxides, which block the sun via physical interruption of UV rays. There are too many organic sunscreen ingredients to describe, but they act to absorb UV radiation before striking the skin. Both are effective when formulated properly. Every practitioner has a preference for one or the other for various reasons.

The same thing applies to ingredients in sunscreens as it does to makeup. Particle size distribution is critical, relative to occluding the skin. When using products with physical sunscreen ingredients, be cautious regarding occlusion. Image 5 on shows a client who has diligently applied a sunscreen with a physical sunscreen ingredient. The bright white appearance is the reflectance of the sunscreen. This is a good thing, but be aware that this could lessen the bioavailability of other active ingredients.

It is rare to see makeup or sunscreen on the skin after use and a subsequent washing. When providing clients with a home-care regimen, including active serums or other products, take a brief history of their product use and to assess if occlusion is present.

Salicylic acid. Salicylic acid is present in many formulations and is an excellent active ingredient to suppress oil production and act as a keratolytic agent and anti-inflammatory. It also tends to stay on the skin surface, albeit in lower concentrations, and is a more porous film on the skin than others. Image 6 shows the skin of a client who has just undergone a salicylic acid infusion on her skin. It looks somewhat normal with no remarkable features. Image 7 is an image of the same client utilizing the color ultraviolet imaging system. Salicylic acid fluoresces and the deposition features are shown clearly. It remains present on the skin after several washings due to its oil soluble nature. Again, while a good thing in certain applications, a slight film of salicylic acid is left and reduces the bioavailability of the active ingredients in skin care treatment.

While there are many reasons why products with known efficacious active ingredients often show inconsistent results on different clients or even the same client over time, bioavailability of active ingredients is one well-known cause. To ensure maximum bioavailability of skin care products and their benefits, a clear understanding of the sources of potential interference that a variety of products can create on the skin surface is critical to client care.

Product occlusion can be demonstrated from cleansers with waxy alcohols, makeup via pigment particle size distribution and binders, sunscreens with physical UV blocks, and finally, salicylic acid. Being aware of the interference from occlusion and its source can help skin care professionals deliver a more effective product regimen for your clients and help them to achieve a more consistent and effective skin quality.


Robert ManzoRobert Manzo, president of Skinprint, has more than 30 years experience in creating efficacious health and beauty products.




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