 There are several mechanisms by which HBOT may elicit analgesic effects. There is a growing body of evidence that HBOTs analgesic effect related to nitric oxide metabolism and endogenous opioid secretion. Furthermore, the inhibition of tumor necrosis factor alph TNF-α, the production of substance P, and the modulation of serotonergic pathways have all demonstrated a modification in the pain response following HBOT. In animal studies HBOT decreased allodynia and hyperalgesia in different models of neuropathic and inflammatory pain. The long lasting antinociceptive effect of HBOT was found to be dose-dependent in non-injured tissues. 