Methylene blue is the latest influencer biohack trending online, promoted as a miracle health supplement for more energy, sharper focus and a stronger immune system. Some even claim it protects against cancer. But experts warn that methylene blue can cause serious side effects and poses real risks if taken without medical supervision. Despite the hype, there is no scientific evidence that this dye works as a dietary supplement — and buying it online can be dangerous. Health myths like this are not new. Is coffee really bad for the heart? Should you rest when you have back pain, or move more? And are e-cigarettes actually healthier than smoking? DW's In Good Shape investigates viral health trends and long-standing beliefs — and explains what science really says