"Unpacking the Science: Exploring the Unique Physiology of Black Skin and Melanin"

This article was developed completely by accident in a way. It actually started as an article about taking proper care of skin of different colors. As I researched the section about black skin, I found that we actually don't have as much scientific information specifically for black skin. This article is definitely just a starting place and i encourage everyone that's interested to do their own research. I always say that skin is just skin but what i did not know is that there are more differences than just color.

Stratum Corneum Composition and Function

Black skin has a different composition than other skin colors (obviously). However, this is true in more ways than the apparent. The stratum corneum is the outermost layer of the epidermis (outer 20 µm to be specific). This layer of skin is qualitatively described as a brick and mortar structure. Corneocytes are flattened keratin filled cells that lack cytoplasmic organelles (functional organs) and are the bricks. Essentially they are dead keratinocytes. A specialized group of epidermal fats, half of which are ceramides, forms the mortar. These essentially work together to form your skin barrier.

Corneocytes have high mechanical strength and also carries melanin that gives skin its color. corneocytes acts as a tough physical, chemical and immunological barrier. The fatty lipid compounds acts to improve barrier function of the skin and will be referred to as ceramides from here on out. Ceramides act to hold skin cells in a tight bond and ensure that trans epidermal water loss does not occur too fast. This is a very basic description however.

While most skin colors have similar stratum corneum (SC) thicknesses, black skin has more cell layers that are more cohesive than other races. This may suggest the presence of a stronger SC barrier and faster recovery from barrier damage. This is the source of the myth that black skin is thicker when instead it is more accurate to say that it is denser. Black skin has also been shown to have a lower overall ceramide content. Because of this, black skin also has more transdermal water loss than other skin colors. This low ceramide content could possibly be due to having more layers of corneocytes in the same space however, the actual reason for this has not become apparent to me during my own research.

Black skin exhibits higher (2.5x higher) spontaneous desqaumation rates than that of lower phototypes. Desquamation, also known as skin peeling, is the process of shedding dead skin cells from the body's surface and replacing them. It's a vital protective mechanism that removes harmful agents, microorganisms, and damaged corneocytes from the skin. However, an increase in the rate of desquamation or the amount of skin cells shed can lead to dry scaly patches of skin. While I have not personally seen anything that particularly connects the lower ceramide count of black skin to its higher desquamation rate, I simply cant help but to be lead to that very thought.

The differences exhibited between skin of different colors is apparent in the stratum corneum because we can clearly see some of them. The next question is how do these differences happen. To answer that you must look to the stratum basale where melanocytes reside.

Stratum Basale and Melanin Development

The Stratum Basale is the lowest level of the epidermis layer of skin. It contains a single layer of basal cells. Some basal cells serve to anchor the epidermis. Others behave like stem cells and divide to create keratinocytes. In the end the keratinocytes will die and become corneocytes. In the meantime, they play a vital role in wound healing and immune system response to wounds and microorganisms. Also in this layer of skin are merkel cells which are touch receptors. For this article, the important point here is that this is where melanocytes reside in the skin. Melanocytes produce melanin and regulates transfer to keratinocytes.  Each Melanocyte can extend up to 40 dendrites that connect to keratinocytes to "inject melanin" in them. This transport process is not clearly understood and there are 4 or 5 theories as to how this is accomplished. These melanin carrying keratinocytes then move upward toward the skins surface until they die and all the layers above it have shed. They then become corneocytes in the stratum corneum.

There are actually 5 types of melanin. For pigmentation of skin, melanin comes in 2 forms eumelanin and pheomelanin. Eumelanin is further divided into black eumelanin and brown eumelanin. Pheomelanin is yellow to brownish red. Eumelanin is UV absorbent and very photostable. While pheomelanin is photounstable and can even cause carcinogenesis. This is why lighter skin is more susceptible to skin cancer. While black people are susceptible to skin cancer it usually only occurs in areas where pheomelanin exists in higher amounts (i.e palm of hands and bottom of feet).

Skin colors and shades are determined by the mixture of brown eumelanin black eumelanin and pheomelanin. While humans generally have the same number of melanocytes, the output of these melanocytes is what determines hair and skin color. For instance blonde hair is a result of a little brown eumelanin in the absence of black eumelanin. Strawberry blonde hair is the same as blonde hair but with pheomelanin in the mix. Black hair consists of black eumelanin. Essentially, the mix of melanin determines the color of hair and skin. Color intensity is determined by how melanin is contained. Melanin is housed within a membrane that is believed to be specifically used in keratinocytes what will be referred to here as a melanokerasomes. Lighter skin colors tend to have multiple smaller melanin molecules within a single melanokerasome while darker hues have melanin that is large and singularly encased within a melanokerasome. In either case the melanokerasomes are the same size.

Regardless of the type and amount of melanin it is always positioned right above the nuclei of keratinocytes to protect DNA within from photodamage. As a reference, the darkest skin has a protection value of SPF-13. The point here is that the differences occur because of genetic and environmental variances that result in completely different skin. Its not just differences in color but also in structure, composition and associated complications.

Your Melanocytes are given to you from the neural crest as an embryo and is the result of the genes of your ancestors and their overall multi-generational sun exposure. That story is the same no matter what the race. Essentially the melanin production blueprint was passed down to you and can be slightly altered by environmental factors. Sunlight exposure, for example, will signal for melanocytes to produce more melanin making skin darker. These differences are expressed in skincare requirements. One example would be that while everyone should wear sunscreen the priority however, may be much higher for a fair skinned person than a dark person. This article is definitely only a starting point as I tried to keep this article under a 5 minute read. However, I encourage everyone to research and discover more about what makes your skin special. Be sure to use the knowledge contained herein to take better care of the gift wrapping (skin) that your ancestors gave you.