Robert F Kennedy Jr may be a fan of methylene blue—which is one of the "best-kept secrets of biohacking". The 71-year-old was recently seen adding drops of mysterious blue liquid to his glass mid-flight. Though he wasn't seen drinking it later, the clip — shared on X by the account American AF— quickly went viral, racking up over 20.4 million views. For the uninitiated, Kennedy Jr has been nominated by US President Donald Trump to lead the Health and Human Services in his second term.What Is Methylene Blue?Methylene blue is a medication that is used to treat methemoglobinemia, which is a rare blood condition that affects how rare blood cells deliver oxygen throughout the body. Scientifically called Methylthioninium chloride, it is an organic thiazine-type compound with a dark blue-green colour and crystalline structure. Intrestingly, methylene blue was synthetically prepared for the textile manufacturer Heinrich Caro in 1876. However, its medical benefits began to catch the eye of researchers in the 1980s, particularly as a malaria treatment. Clinical practice and laboratory use began only in 1890. What Are Its Other Benefits?In recent years, celebrities, wellness influencers and biohackers have touted methylene blue for several off-label uses. While there is limited research on this, celebrities have claimed that it can boost energy levels and metabolism, enhance cognitive function and combat ageing. Early research suggests that it may also have antioxidant properties that help reduce toxic proteins in the brain, potentially aiding in the prevention of neurodegenerative diseases like Alzheimer’s and Parkinson’s. Some studies also indicate that the drug may help delay skin ageing by stimulating the production of collagen and elastin, reducing cellular damage and promoting wound healing. However, experts caution that more research is needed to determine if it is both safe and effective for these purposes.Are There Any Side-Effects Of Methylene Blue?The toxic effects of the application of this substance are dose-dependent and include serious symptoms such as hemolysis, paradoxical methemoglobinemia, nausea and vomitus, chest pain, dyspnoea, and hypertension. These adverse effects will manifest at doses exceeding 2–7 mg/kg.63,64. Moreover, refractory hypotension and skin discolouration were documented upon administration of 20–80 mg/kg. A study published in Toxicology Research (Camb) on August 30, 2022, revealed that Methylene blue (MB) is a type of drug that temporarily blocks an enzyme called monoamine oxidase A (MAO-A), which helps regulate brain chemicals. Even in tiny amounts, MB can affect this enzyme. When given through an IV at 0.75 mg per kg, it reaches high levels in the brain, increasing serotonin—a key mood-related chemical. However, too much serotonin can be dangerous, especially when combined with antidepressants like SSRIs and SNRIs, potentially leading to severe side effects like hyperactivity.