Cosmetic Serum-what is it?

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Words from an Expert

We read about age defying products where ever we look. We are usually drawn to those tiny little expensive vials that say ‘Serum’.There are numerous products in the market to help us maintain hydrated and youthful skin and serums are certainly top on the list. 


So what is a serum?
Let’s take the mystique out of this magical little potion that Rip Van Winkle will happily endorse, or is it Rip Van Wrinkle? Just kidding.

What is a serum and what are the benefits?

In cosmetic dermatology and clinical dermatology, rarely is a chemical applied to the skin in its pure state since this will cause serious skin irritation and internal toxicity. In order to deliver an ‘active’ substance (a substance that is intended to produce a beneficial effect on target tissue/cells), it must be delivered with the help of a ‘carrier system’, a ‘vehicle’, or a ‘base’.

This carrier system works like a courier, delivering the actives effectively, safely and in a targeted fashion to the target tissue. It has been shown through rigorous scientific research that the vehicle carrying the actives plays a vital role in the treatment process. Without a carefully designed vehicle specific to the active ingredient of a formulation, treatment is deemed useless and ineffective.


The burning question is this: How much does our skin really absorb? And it is this question that fuels the cosmetic industry that is constantly striving to formulate cosmetics that will penetrate the skin barrier (trans-epidermal route) and produce the desired effect at a deeper level. Skin absorption dynamics are complex and it would take me several pages to write about the various factors that influence percutaneous absorptio.

A lot of variables are involved (morphological, environmental, chemical, biological and physiological), including an individual’s age, overall health, level of skin dryness, health of skin and area of skin where substance is applied. Various studies indicate that absorption of topically applied substances will depend upon the physical and chemical properties of the ‘carrier’ molecules and ‘actives’ themselves.There is a popular myth that states that a lot of what we apply to our skin is absorbed into our body. This does not hold scientific validity since the primary function of the skin is the barrier function, and it is not easy to quantify exactly how much topical substance is absorbed into the skin without having examined every aspect of the absorption equation. Having said that, one must remember that even though healthy skin is highly impermeable it is however porous and will allow substances of low molecular weight (less than 500 Daltons to be specific) to pass through

A historically important study by Schwenkenbecher in the early 1990’s concluded that the skin is permeable to lipid soluble substances and gaseous material but practically impermeable to electrolytes and water. Thousands of scientific studies examine trans-epidermal absorption science through various mathematical calculations that take all these different variables into account. One key study mentioned in the British Journal of Dermatology (BMJ) concludes that ‘risk assessment following topical exposure to cosmetic and dermatological formulations cannot be precisely evaluated.’ The science of skin absorption dynamics is lengthy and beyond the scope of this discussion, but I have summarized key points that can be applied to practical life.

t is important to note that unhealthy skin, broken skin, and certain diseases like eczema or irritant dermatitis will impair this barrier function and absorption of substances through skin will be pronounced. Therefore, the important point to remember is that even though there is non-conclusive and conflicting evidence as to the exact percentage of how much is absorbed through intact human skin, the skin does allow substances below 500 Daltons to pass through and disease can weaken the barrier function, so we must be careful about what we apply to our skin and not take any chances.

In this modern age, the science of formulation has advanced dramatically and vehicle design has become complex and highly intricate. The main purpose of the carrier system is to keep the actives chemically stable, maximize efficient epidermal penetration and deliver the drug or active ingredient to the site of action, thereby limiting unwanted side effects or systemic effects and maximizing efficacy.Treating skin issues via a topical mode of application means that there is an intimate contact of the active ingredient with the target tissue, in this case, the skin.To ensure maximum penetration of the actives, the molecules within the serum must be very small. The smaller the size of the molecules, the more effective the desired effect. Anything above 500 Daltons will just sit on top of the skin without ever penetrating the stratified epithelium and will be eventually washed away by sweat or water. You may have often tried various skin care products that have resulted in little to no benefit. This is why. They never reach the site of action and your money has been going down the drain all this time. So be wary of brands that use false advertising practices and use low quality and insufficient concentrations of ingredients that are basically no good.Unfortunately a lot of the allergens and certain toxins have a molecular weight of less than 500 Daltons, thus resulting in undesirable systemic effects. Cosmetic manufactures use this scientific measurement to their advantage and develop more efficient smaller molecules that will effectively pass through the tough cornified epithelial barrier.A serum is one such carrier system. It is designed specifically to deliver the active component of the formulation in its purest state, in very high concentrations. Therefore when you use a serum, remember you will require a very small amount, since the actives are in high concentration and tiny amounts will achieve dramatic results.Another aspect of a serum is that because it is so effective in penetrating the epidermal barrier (trans-epidermal route), the active ingredients can be delivered deeper into the skin and produce a targeted action at a cellular level. Hence, every serum is unique and designed with a specific action in mind.There are serums for lightening skin, for smoothening out wrinkles, for decreasing large pores, for tightening and firming the décolleté area, for contouring, for treating delicate eye wrinkles and for any other skin condition that requires intensive targeted treatment.

Serums are helpful since they are highly permeable and it is due to this property that makes a serum extremely useful as a vehicle when developing anti-aging products.


The cosmetic industry has become highly innovative and has started mimicking in-office treatments like collagen boosters, ampoules and infusions. Boosters, infusions, ampoules and essences are similar to serums and contain high concentrations of focus ingredients and are capable of delivering powerful results. There are slight differences between all these little giants and we will tackle them in our next article.

So next time you buy a serum, just remember that a small amount will go a long way!

Dr.Ansul N Khan
Founder of Cuticonscious
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