This is still under investigation but looks promising, including in the treatment of "long" COVID
The Perrin Technique™ is an osteopathic approach developed in 1989, originally for ME/CFS, that aims to manually drain toxins from the cerebrospinal fluid into the lymphatic system. Movement of the spine and massage of the soft tissues in the head, neck, back and chest direct all the toxins out of the lymphatic system and into the blood, where they are eventually detoxified in the liver.
Eventually, with less poisons affecting the central nervous system, the hypothalamus and the sympathetic nervous system begin to function correctly, restoring health to the patient
https://theperrintechnique.com/
