Light in the red and near-infrared ends of the spectrum accelerate healing in all cells and tissues. One of the ways they accomplish this is by acting as potent antioxidants. They also inhibits nitric oxide production.
Can red and near-infrared light prevent or reverse hearing loss?
In a 2016 study, researchers applied near-infrared light to auditory cells in vitro before placing them under oxidative stress by exposing them to various poisons. After exposing the pre-conditioned cells to chemotherapy poison and endotoxin, study researchers found that the light altered the mitochondrial metabolism and oxidative stress response for up to 24 hours post treatment.
“We report a decrease of inflammatory cytokines and stress levels resulting from NIR applied to HEI-OC1 auditory cells before treatment with gentamicin or lipopolysaccharide,” wrote study authors.
Results of the study showed that pre-treatment with near-infrared light reduced the pro-inflammatory markers associated with increased reactive oxygen species and nitric oxide.
Study #1: Can Red Light reverse Hearing Loss?
The effect of near-infrared light on hearing loss following chemotherapy poisoning was evaluated. Hearing was assessed following gentamicin administration and again after 10 days of light therapy.
On scanning electron microscopic images, “LLLT significantly increased the number of hair cells in middle and basal turns. Hearing was significantly improved by laser irradiation. After LLLT treatment, both the hearing threshold and hair-cell count significantly improved.”
Study #2: Can Red Light reverse Hearing Loss?
In this study, rats were exposed to intense noise in both ears. Afterwards, their right ears were irradiated with near-infrared light for 30 minute treatments everyday for 5 days.
Measurement of the auditory brainstem response revealed an accelerated recovery of auditory function in the groups treated with LLLT compared with the non-treatment group at days 2, 4, 7 and 14 after noise exposure. Morphological observations also revealed a significantly higher outer hair cell survival rate in the LLLT groups.
Looking for indicators of oxidative stress and apoptosis in untreated vs treated cells, researchers found “Strong immunoreactivities were observed in the inner ear tissues of the non-treatment group, whereas these signals were decreased in the LLLT group at 165mW/cm(2) power density.”
“Our findings suggest that LLLT has cytoprotective effects against NIHL via the inhibition of iNOS expression and apoptosis.”
Study #3: Can Red Light reverse Hearing Loss?
In a 2012 study, nine rats were exposed to loud noise and the use of near-infrared light on hearing recovery was tested. The day after loud noise exposure, the left ears of the rats were treated with near-infrared light for 60 minutes for 12 days in a row. The right ears were untreated and considered the control group.
“After the 12th irradiation, hearing threshold was significantly lower for the left ears compared to the right ears.” When observed using an electron microscope, the number of auditory hair cells in the treated ears was significantly larger than that of the untreated ears.
“Our findings suggest that low-level laser irradiation promotes recovery of hearing thresholds after acute acoustic trauma.”