Science of Beauty — The Basics: Science of Skin

Why do you need to understand the basic science of skin?

Most cosmetics are applied to either the skin or hair, so by understanding the basic science of either will enable you to become a better cosmetic chemist. You’ll have a better understanding of how topical products can work, and you will be able to formulate products based on your target — whether it’s sensitive skin, acne-prone skin, etc.

What is skin?

Skin is the largest organ of the body and its main purpose is to act as a threshold between you and the outside world. It keeps things in while keeping things out & helps with maintaining homeostasis. Lipids & moisture IN, pollution & bacteria OUT (not literally, but literally).

Think of it like a brick wall where only things of certain sizes can squeeze in or come out, while preventing other things from penetrating.

Layers of Skin:

  1. Epidermis — outermost layer (Is your epidermis showing? Haha, I sure hope it is.)
    • stratum corneum – the layer of skin that cosmetic products are applied on!
      • skin cells here are dead and continually shed from the skin’s surface
      • the thickness of this layer varies based on location: e.g. your eyelids vs. your heel
    • melanocytes – produces the pigment known as melanin that gives skin its color and protects against UV rays
    • basal cell layer – cells here are continually dividing to produce new skin cells and move towards the skin surface (stratum corneum) to replace dead skin cells
  2. Dermis — the middle child layer
    • contains connective tissue in the form of collagen and elastin – proteins that keep the skin firm and strong
    • hair follicles, nerves, lymphatic vessles, sebaceous glands, and sweat glands also reside in this layer
  3. Subcutaneous (fat cushion) — innermost layer
    • comprises mainly of adipose (fat) which provides protection from injury, produces heat, and serves as a cushion for the body attaching the upper layers of skin to the bone and muscle below

Different Skin Types:

  1. Normal skin
    • balanced skin, little to no skin conditions or problems
  2. Dry skin
    • typically has a more alkaline pH
    • doesn’t produce enough sebum (skin’s natural oil)
    • can often look flaky or feel tight and itchy
    • may benefit from the use of creams, facial oils, products that contain AHAs to gently exfoliate, and products that contain hyaluronic acid
  3. Oily skin
    • over-production of sebum
    • P. acnes loves sebum, so people with oily skin can be more prone to acne
    • may benefit from products that are non-comedogenic, products containing BHAs for mild exfoliation, mild facial cleansers, & products that contain niacinamide
  4. Combination skin
    • having both dry and oily skin at the same time, or having either or depending on the season
    • at the same time: most people have an oily “t-zone” and are dry everywhere else — may have to use different products on different parts of the face depending on the condition
    • season: dry skin during the winter & oily skin during the summer — may have to use different products to combat the skin type during the different seasons
  5. Sensitive skin
    • people with sensitive skin are more prone to irritation or inflammation which can occur through use of certain products or ingredients.
    • sensitivity can be due to fragrance allergies or low/high pH products
    • may benefit from mild facial cleansers, fragrance-free products, & products containing anti-inflammatory ingredients

All skin types can benefit from these basic necessities: using a gentle/mild facial cleanser, a moisturizer (one fit for your skin type), & sunscreen (at least SPF 30).

Skin in Relation to pH & Cosmetics

Sebum and sweat make up what is called the acid mantle on top of the stratum corneum. Again, this acts as a threshold or barrier that serves a protective function for our body to function. As the name ‘acid mantle’ suggests, the pH of skin is slightly acidic — pH ranging from 4.0-6.0 depending on the skin condition and location (this is actually a much larger pH range than most would suggest).

If the pH of our skin is slightly acidic, wouldn’t it make sense to apply cosmetics that have a similar pH range? Consistent use of products outside of our typical pH range could potentially disrupt the normal function of our acid mantle — causing potential skin irritation/inflammation or even causing our skin to be more prone to certain bacteria (say, p.acnes). Basically, our skin becomes more prone to damage and infection.

However, there are times where you can and should formulate products outside of this pH range for efficacy purposes. For example, when formulating with alpha hydroxy acids (AHAs), the pH of the final product can have an impact on the overall efficacy of the product. The product may require it to be at a lower pH than most typical cosmetic products for the AHAs to have a better exfoliating function.

As a cosmetic chemist, not only do you have to think about the science of skin when you are formulating, you also have to think about how to make the product most effective.

Note: A more in-depth version of skin in relationship to cosmetics will be included in COSCI 102 – The Intermediate.

Look forward to the next sections of COSCI 101 – The Basics: Cosmetic Padacts

Continue learning about the basics of cosmetic chemistry with Cosmetic Padacts in the next sections of COSCI 101. Get information on hair chemistry and more in-depth information on topics in cosmetic chemistry. Follow us on Instagram (@cosmeticpadacts) & Facebook for updates on upcoming posts.

Comment below if you found this post helpful or if you have any questions. You can also submit comments/questions through the Contact tab or directly e-mail:  Thank you for being a part of this journey!

– Cosmetic Padacts

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