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Low-level laser therapy (LLLT) has been used for more than 20 years in Europe and was later introduced in the United States as a possible option for pain relief and postsurgical tissue repair. Proponents suggest that red and near-infrared light may support tissue healing, possibly by stimulating mitochondria to increase adenosine triphosphate production.
Human studies examining LLLT for hearing loss and tinnitus have reported mixed results; some observed modest improvements in hearing thresholds or tinnitus symptoms, while others did not.
Thirty-five adults enrolled. Two withdrew because of lost interest or scheduling issues, and data from three others were excluded: one provided unreliable audiometric/speech scores, one with profound loss could not complete speech testing, and calibration errors affected the third. The remaining 30 participants were analyzed. The University of Iowa Institutional Review Board approved the protocol, and all gave written informed consent.
An Erchonia EHL laser delivered the light. The portable unit comprised a main body and a hand-held probe with two diodes: green (532 nm) and red (635 nm), each emitting 7.5 mW (class IIIb). Lenses converted the beams into parallel lines rather than spots. An identical-appearing placebo unit contained non-functioning light-emitting diodes instead of lasers.
Participants were pseudorandomly assigned to treatment, placebo, or control groups. Initial randomization was occasionally adjusted to balance group size, sex ratio, mean age, and mean pure-tone thresholds. The treatment group received active laser application; the placebo group followed the same protocol with the inactive device; the control group made equivalent visits without any intervention. A repeated-measures design compared pre- and post-test batteries.
Data from both ears were combined after visual inspection revealed no obvious left-right differences. Pooling ears may violate independence assumptions and could inflate the effective sample size, increasing the chance of detecting a significant effect. All tests used α = 0.05.
PubMed search for LLLT and auditory studies
No statistically significant effect of LLLT on auditory function was detected by pure-tone audiometry, speech understanding, or TEOAEs in this study, and no individual participant experienced a clinically meaningful change. It remains possible that other LLLT protocols could influence hearing; the device selected may not have been optimal for this application. Additional work to clarify the anatomic and physiologic mechanisms of LLLT on the auditory system is warranted before further clinical trials are pursued.
