PEER-REVIEW | DERMATOLOGY | which is responsible for the variable reaction of the
skin to different physiological and pathological situations. The racial characteristics of the skin are also responsible for the disparities in the transcutaneous absorption of drugs and lotions13,14
. The properties of the skin among the
predominant problem for lighter skin individuals, while mottled pigmentation and uneven skin tone are predominant for darker skin types.
.
different races were investigated in great detail in the past. The content and distribution of pigments is the most important factor that determines the primary variation amongst the races. This variation depends on many factors, such as quantity of melanin, melanosome content, type of pigment, and the extent of UV exposure. The light colour in Caucasians is mainly due to haemoglobin and oxy-haemoglobin, whereas carotenes can be a source of yellow hue in some races. The shades of brown and black colours are produced by varying amounts
Wrinkling is the
of melanin and its distribution in the skin. The quantity and type of melanin and the dispersion of the melanosomes are responsible for the difference in skin pigmentation15–18
Another important factor that determines the reactive
properties of the skin is the variation in the structure of the stratum corneum19
. Even though some studies
demonstrated the presence of more corneocytes in darker skin compared to lighter skin, there was no significant difference in the thickness between these groups. It has been a constant observation that the cell layers in the dark (Negroid) skin were more compact; leading to a greater intercellular cohesion20–22
. Even though
there was no significant variation observed among the races, the darker skin subjects are shown to have a higher rate of desquamation. The quantity, quality and size of the corneocytes are well correlated with epidermal hyperproliferation and the development of dry skin23–26 The trans-epidermal water loss is the total amount of
.
Table 2 The Fitzpatrick classification of skin SKIN TYPE SKIN COLOUR
Type 1 Type 2 Type 3 Type 4 Type 5 Type 6
44 difficulty
water vapour lost through the skin and appendages under non-sweating conditions. Several studies compared the trans-epidermal water loss among different races27
. It has been reported that trans-epidermal water
White; very fair; red or blond hair; Always burns, never blue eyes; freckles
SKIN CHARACTERISTICS tans
White; fair; red or blond hair; blue, Usually burns, tans with hazel, or green eyes
Cream white; fair with any eye or Sometimes mild burn, hair colour; very common
gradually tans
Brown; typical Mediterranean caucasian skin
Black Rarely burns, tans with ease
Dark brown; mid-eastern skin types Very rarely burns, tans very easily
Never burns, tans very easily
loss is greater in darker skin compared to fair skin. Studies on Asian subjects were variable. Similar studies on the water content of the stratum corneum revealed variable outcomes27
. Apart from the pigmentation and melanosome content,
variations in the dermal structures were also observed among the races. The dermal structure, viscoelasticity properties, and the distribution of the skin appendages differ among ethnic groups. Darker skin types have a larger pore size, increased apocrine glands and secretions with the highest level of microbial flora. The ceramide levels of the skin are related to moisture and the protective function of the skin. It has been shown that Asians have
January/February 2016 |
prime-journal.com
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