The earth itself has a very strong magnetic field, so there is an adaptation and even dependency on magnetism. A weak and stable magnetic field is good for the body, and magnetic therapy is often used in medical treatment. Electromagnetic wave is different, it is a kind of high energy wave, its frequency can produce undesirable effect to the body. So the magnet is harmless to the human body.
The flexible magnets is neither harmless nor beneficial to the human body. There is nuclear magnetism in medical equipment, high magnetic field has 3T above, no harm to human body. It is generally accepted that nuclear magnetism is the safest in all radiology medical devices. That is to say, people are not afraid of the magnetic field, they are more afraid of radiation. The high magnetic field does have a certain negative effect on the human body, but the magnetic content of the flexible magnets is limited, and it can't affect the human body at all. It is claimed that magnets provide the magnetic force that changes the physiology of tissue, and that each cell has a positive and negative polarity, and some claim that the magnet can improve blood circulation. In fact, there is no evidence that the human body tissue cells or blood and magnetic field have any interaction, the iron ions in red blood cells, instead of ferromagnetism, or even reverse magnetic, not attracted by magnetic field.
Don't worry about the flexible magnet, it safe enough to use in any place.