<s>[INST] My 10 year old daughter has the black marking around her neck and under her arms she has been tested 3 times for diabeates because of her weight gain. Everytime it comes back negative. How do I get rid of this and should I have further testing done on her [/INST] Hi...this is called acanthosis nigricans and the only way to get out of it is to lose weight and get back to normal weight for age. NO medicines are there to decrease this black discoloration over the neck. This is related to obesity and will become normal once normal  weight is restored.Regards - Dr. Sumanth </s>