Mild traumatic brain injury (mTBI) is the most common traumatic brain injury affecting military personnel. mTBI is associated with several neurological symptoms that correlate with neuroinflammation. One of the neurological symptoms associated with mTBI is pain. mTBI-induced pain may be challenging to manage in some cases. Therefore, opioids may be used to control such pain. However, opioids have significant side effects, especially when used chronically, which may lead to substance misuse. The opioid crisis has demonstrated the need for complementary methods for pain control. Because of the association between mTBI and substance misuse, there is a significant need for alternative/complementary approaches to opioids to treat pain, especially in treating the pain associated with mTBI. mTBI induces inflammation as manifested by increased inflammatory cytokines such as IL-6 and TNF-α in the central nervous system (CNS) and plasma. Two sources for these cytokines are microglia and astrocytes, both of which become activated after mTBI, contributing to the development of pain. Decreasing the levels of pro- inflammatory cytokines and increasing the levels of anti-inflammatory cytokines may promote decreased mTBI- induced pain. A therapy that reduces microglia and astrocytes' activation and decreases the neuroinflammatory environment would be ideal for both military personnel and veterans. Phototherapy is used for multiple medical conditions, but few studies investigated the effects of phototherapy on pain. We have shown that green light exposure (GLED) was antinociceptive by reversing thermal and mechanical hypersensitivity in rats. In humans, we have demonstrated that GLED decreased chronic pain and sleep disturbances in fibromyalgia and migraine, suggesting that GLED therapy applies to humans despite differences in the visual systems between rodents and humans. Furthermore, we have shown that GLED reversed the hypersensitivity associated with mTBI in two different TBI mice models. We also demonstrated that GLED reversed postsurgical thermal and mechanical hypersensitivity by increasing anti-inflammatory IL-10 levels in the cerebrospinal fluid (CSF) while decreasing pro-inflammatory IL-6. GLED reversal of thermal and mechanical hypersensitivities was attenuated when the periaqueductal gray (PAG), a crucial pain-modulating center, was blocked, suggesting that GLED may be inhibiting the descending pain-facilitatory pathway. Therefore, it is reasonable to postulate our hypothesis that GLED visual exposure will attenuate mTBI- induced hypersensitivity by inhibiting the descending pain-facilitatory pathway. We will use three specific aims (SA) to investigate our hypothesis. SA1 will explore the potential translation of GLED therapy by exploring its ability to reverse the mTBI-induced thermal and mechanical hypersensitivities in multiple rodent sexes and species. SA2 will evaluate the effects of GLED on modulating glial cells and the effects on neuroinflamma...