If elevated levels of anti-streptococcal hemolysin “O” are found, it generally indicates the presence of group A hemolytic streptococcal infection in the body and requires immediate medical attention to further investigate the cause. Group A hemolytic streptococci are a common group of human infections with strong antigenicity. When humans are infected with group A hemolytic streptococci, streptococcal hemolysin “O” will stimulate the B lymphocytes in the body’s immune system to produce the corresponding antibodies, namely anti-streptococcal hemolysin “O”, the level of which can be found to be elevated by blood tests. Current research has found that a variety of diseases are associated with infection with group A hemolytic streptococci, such as rheumatic fever, rheumatic heart disease, scarlet fever, infective endocarditis, and streptococcal-associated nephritis. Therefore, the level of anti-streptococcal hemolysin “O” is helpful for the diagnosis and treatment of these diseases. However, elevated anti-streptococcal hemolysin 0 does not always cause discomfort in patients. Although many patients are infected with group A hemolytic streptococci, the degree of infection is mild and the body’s immune system is effectively controlling the infection, and these patients have elevated anti-streptococcal hemolysin “O” levels on blood tests, but almost no discomfort. Therefore, once the level of anti-streptococcal hemolysin “O” is found to be elevated, there is no need to panic, and it is necessary to go to the hospital for further investigation of the possible causes.