The onset of the vitiligo is due to destroying melancytes on the epidermis layer of skin. Usually the venonat will not get involved. So after the irradiation by the UVA, the melancytes will start to multiply from the melancytes part. and than it transfer to pars infundibularis along hair follicle, finally it will spread over to the near of keratinocyte surroundings. And in clinic we always can see that the pigment always appear on the hair follicle surrounding first.
It can also make the local skin have inflammatory reactions which can destroy the sulfhydryl compound in skin and releasing the inhibiting effect to tyrosinase. And stimulate the activity of the tyrosinase, catalyze formation of the melanin. It can also inhibit pathologic T lymphocyte, or restrain langerhans cells multiply. So that inhibits the local immunity action.
The melancytes can divide and multiply by stimulated under UV light, and increase the formation of the melanin. It also can facilitate the residual melancytes convert from reduced to oxidation type on the white patches area make the melancytes spread.
Besides that, we have to note some important aspects as well.
1) We have to protect our eyes, and wear the glass that can protect the UV light.
2) We should cover the non-lesion part by using opaque materials.
3) Protect skin irritating by sun light, after taking psoralen eight hours protect sun light protected by clothes or broad-spectrum sunscreen such as benzene ketone.
4) Regularly do the routine test such as live an d kidney and eyes examination.
5) Avoid using some photosensitizer at same time such as sulfanilamide, sulfur, acyl urea, consult, phenothiazine and tetracycline derivatives
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