Published on Sep 28, 2016 and last reviewed on Oct 10, 2019 - 2 min read
Though ultraviolet radiation induced erythema is seen in all skin types, it is more marked in fair skin and barely perceptible in dark skinned individuals. This article throws light on different skin phototypes and tanning.
Tanning or skin pigmentation that occurs after sun exposure depends on the individual skin phototypes. The tanning response depends on the wavelength of light inducing it. Immediate tanning is mainly due to ultraviolet A (UVA), whereas delayed tanning is due to ultraviolet B (UVB).
Skin phototypes, also known as Fitzpatrick skin phototypes have different characteristics on exposure to ultraviolet radiation.
The skin phototype categories are:
Type I - Always burn and never gets tan. Seen in individuals with pale white skin, blond or red hair, blue or green eyes.
Type II - Usually burns and sometimes get tanned. Seen in individuals with fair skin, blond hair and blue eyes.
Type III - Sometimes burns, usually tans. Seen in individuals with white skin, brown hair and brown eyes.
Type IV - Burns and always tans. Seen in individuals with light brown skin, brown or black hair.
Type V- Moderate constitutive pigmentation.
Type VI - Marked constitutive pigmentation.
This is primarily due to UVA, longer UVB and also short wavelength visible radiation. It begins soon after exposure to ultraviolet radiation and lasts for up to two hours. Immediate pigment darkening protects the skin against other UV induced effects such as damage of basal cell nuclei.
If any pigment persists for more than two hours, then it is referred as persistent pigment darkening and may last for up to 24 hours. Persistent pigment darkening is usually seen with higher UVA. There is no increase in the number or activity of melanocytes, but there is photo-oxidation of pre-existing melanin with redistribution of pre-existing melanosomes.
In delayed tanning, the spectrum of UV radiation depends on the color of skin.
If there is an increase in the number and activity of melanocytes, then UVB induced delayed tanning has its onset within 72 hours after exposure and it persists for several weeks. While the UVA induced changes occur earlier that is 3 to 24 hours, it overlaps with immediate pigment darkening and lasts for several days.
The UVB induced tanning raises the minimum erythema dose of the skin and it is associated with thickening of the stratum corneum. Thus, it offers a two-fold photoprotective effect whereas UVA induced changes are less photoprotective.
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