There are some differences in the structure and function of the skin among different skin tones; some are more sensitive to the sun and irritation, some are more prone to hyperpigmentation, some experience sagging earlier in life; however, we are all prone to these skin conditions regardless of our ethnic skin type but the rank order of each skin problem is a little different for various skin tones. It is important to understand the structural differences among the skin of different colors to better know your skin needs and treat your skin accordingly.
Structural differences in different skin colors
a. Skin pigmentation
- Melanin content: The first difference in skin characteristics is pigmentation. Variations in the skin melanin content depends on both genetics and UV exposure. Melanin is a natural skin pigment which has the ability to protect the skin from UV rays. Darker skin has a higher content of epidermal melanin.
- Arrangment and size of Melanosomes: Darker skin also has larger melanosomes than light skin. [1]
- Degradation of melanosome: melanosome degrades slower in darker skin types; however, it has been found the number of tyrosinase molecules in black and white skins are nearly equal. [2]
b. Epidermal Barrier Function
- Number of stratum corneum (SC) cell layers: While the SC of darker skin types contain more cell layers than lighter skin [3] there is a small difference in thickness of the stratum corneum between the two, proving that the SC of darker skin is more compact and has more intercellular cohesion as well. [4]
- Lipid content of SC: a study showed that although the Ceramides levels in black skin is approximately 50% lower than lighter skin [5], the SC barrier function is stronger in people with darker skin.
c. Dermis
- Size and number of Fibroblasts: โDarker skin tones contain larger and more numerous fibroblasts, smaller collagen fiber bundles, and more macrophages than white skin.โ [6]
- Thickness of dermis: The dermis is thicker and more compact in darker skin with the thickness being proportional to the degree of pigmentation.
How different skin tones influence the skin behavior
1. Sensitivity
When skin barrier is impaired, the skin is more prone to irritation and inflammation. While this process is the same for all skin types, studies shown that darker skin is less reactive to irritation comparing to light skin tones. Fair skin is the most sensitive due to a thinner and less cohesive stratum corneum, and disorganization of the elastic fibers in the dermis which happens with aging.[7]
Lighter skin is also more sensitive to sun! Since darker skin tones have higher melanin content, they have higher sun protection and show less sensitivity to sun. [8] There actually is different skin classification systems based on UV sensitivity; the most well known one is the Fitzpatrickโs phototype classification system which describes skin types based on their ability to respond to UV light with burning or tanning reactions.
Fitzpatrick phototype classification (phototypes IโVI) [9]
I: those who sunburn easily and do not tan at all
II: those who sunburn easily and tan with difficulty
III: those who sunburn moderately, have immediate pigment darkening, and tan moderately with 60 minutes of midday sun exposure
2. Hydration and barrier function
Barrier function depends on the whole architecture of the SC, so both cohesion of cells and lipid levels determine the strength of skin barrier. Generally, the SC of fair skin is thinner and less cohesive so the barrier is weaker and it is more prone to dehydration.
3. Skin Aging
Though all skin types experience skin aging, the severity and signs of aging often varies based on ethnic origin because of underlying structural and functional differences. People with dark complexions contain a type of melanin known as eumelanin which can provide a stronger resistance to UV rays than the kind produced by paler skins so darker skin usually show the clinical signs of aging at a more advanced age compared with lighter skin tones; typically10 to 20 years later. [10]
Sun exposure is the major reason for the development of wrinkles and since darker skin has more melanin and a stronger barrier so it is more resilient to the environment and UV rays, and signs of aging appear less pronounced and start at a later stage (until well into their 50s) on darker skins. Darker skin also has a more compact and thicker dermis, with the thickness being proportional to the degree of pigmentation, so it is likely that this could be the reason that darker skin tones have lower incidence of facial rhytides. [11]
On the other hand, wrinkles and sagging is a predominant concern for lighter skin tones. Since lighter skin is more susceptible to UV damage, it is more prone to wrinkling around the lip area, crowโs feet and under eye and cheek and jawline folds.
4. Hyperpigmentation
While people with darker complexions are the most blessed when it comes to visible signs of aging, hyperpigmentation and uneven skin tone is very common in darker skin types.
Inconsistent pigmentation with both hypopigmentation and hyperpigmentation is a sign of photoaging in people with skin of color. Lighter skin tones have a lower tanning ability when exposed to sun and they tend to burn so hyperpigmentation is less common in fair skin. [12]
Hyperpigmentation and uneven skin tone is not always caused by sun exposure. In darker skin uneven skin tones is mainly caused by inflammation and hormonal imbalances, while lighter skin tones are less prone to post-inflammatory pigmentation.
People from certain ethnicities (Mediterranean, middle east, Indians, African-Americans) are more prone to dark circles and hyperpigmentation in general due to higher levels of melanin in their skin.
Remember though darker skin pigments provide some UV protection, you still MUST wear sunscreen regardless of your skin tone!
Since the structure and function of the skin among different skin tones is a little different, some suggest that our skincare should reflect these differences. Virginia Stone is a brand which has designed eye creams to serve certain requirements for different skin tones. Read my review of her eye creams here.
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