How are you from black to blonde

your consultation isnt clear, kindly explain more about your medical consultation so we can gladly answer you as soon as possible 

Is there any medication to change body color from black to blonde ?
blonde isnt skin color , if you meant by it white skin , then its may possible but there are different options with different success rates and potentional side effects 
Is it perminant ?
no its not , skin will back to its normal color once treatment stopped 
Effective ways to whitening skin or whitening special area of skin :
1. using the products that contain hydroquinone ( need some months to see results )
2. using products that contian vitamin A , retein-A , tazarotin ( need some months to see results )
3. using laser treatment to remove black skin or change skin layer ( effective but need more than one session )
4. using nitrogine treatment to remove black skin ( effective but may need more than one session )
5. use whitening injection to whiten the area directly ( immediet effect but not recommanded ) 
Recommanded product to whiten skin :
1. Olay White Radiance Brightening Intensive Cream
2. loreal whiten products 
3. Kaya Pigmentation Reducing Complex
General advices :
1. consider consult a dermatologist first before start looking for medical treatment and follow doctor instrcutions 
2. use sun block products regularly
3. pay attention to personal hygine 
4. always keep you skin moist