Answered by Shaykh Amjad Rasheed
I have read that tattoos are filthy. Why? How are they removed?
Tattoos are considered filthy in our school and they prevent the validity of prayer. This is because tattooing–according to the explanation of the fuqaha–is extracting blood from the hand (for example) using a needle and then mixing a colored pigment with it that will mix with the blood and then dry so that its substance remains on the outer body.
Tattoos are prohibited (haram) and are obligatory to remove, unless one fears harm thereby, such as becoming sick, or delay in recovery from sickness. In such cases, it would not be obligatory to remove them.
As for how they are removed, this is a matter that returns to medicine, and there is no particular manner prescribed for it by the fuqaha.