There's not much harm. It's just that the tattooed skin is dyed. Tattooing is to stab various patterns and marks on human skin with a needle, and then paint it with ink or various colors to become a symbol that will never fade. From the perspective of modern people, tattooing is a deformed aesthetic mentality with no cultural background at all, because from the medical point of view, tattooing has many harms. Skin is the first line of defense of human body, which can resist the damage of external mechanical, physical and chemical stimuli and the invasion of pathogenic microorganisms and plays an important role in human health. Tattoos, on the other hand, destroy this line of defense, making the human body's ability to resist all kinds of stimuli decline, especially prone to bacterial infection. Most tattoo artists don't know medicine, and the disinfection is not strict or not at all. When the needle tip pierces the skin, bacteria and other pathogenic microorganisms are brought into the body, causing various infectious diseases, such as furuncle, carbuncle, erysipelas and impetigo. If the wound area is large, the bacteria are virulent, or even grow and reproduce in the blood, they will suffer from sepsis and endanger their lives. There are many kinds of pigments for tattoos, many of which are chemicals. These chemicals will cause dermatitis and allergies when they enter the human body, and even make local itching, pain, burning sensation, numbness, etc., and some will lead to cell mutation, which is the prelude to cancer. Tattoos are extremely difficult to get rid of. At present, a special drug has not been developed to remove them. The only way is plastic surgery.