Ear light therapy

Ear light therapy is a woo light therapy method, where earphone-shaped LED lights are inserted into the ear. Ear light therapy is promoted as a stimulating treatment for sleep-related conditions such as jet lag, tiredness in shiftworkers and seasonal affective disorder (SAD, a form of clinical depression caused by low levels of sunlight). The current scientific consensus is that it is ineffective.

Despite lack of effectiveness, ear light devices are nevertheless still sold by Valkee Ltd. under than brand name HumanCharger. The device was approved as a medical device in the EU; however, this simply certifies its safety, such as electrical and thermal safety, but not actual effectiveness.

The origin of the device is in brain research done at the University of Oulu in Finland. The retina of the eye is a type of nerve tissue, so its similarity to brain tissue is expected. In 2011, University of Oulu scientists published a finding that brain tissue contains a light-sensitive pigment called light-sensitive photoreceptor protein (Opsin-3 that is encoded by the gene). This claim was based on studies of cadavers, and has not been published in a peer-reviewed journal. The hypothesis was that if brain tissue is photosensitive, then illuminating it could induce similar effects as illuminating the retina: relief of SAD, jetlag and tiredness. While brain tissue is difficult to access, the bone in the ear canal is thin enough that light can be directly shone through it using regular LEDs. This is a falsifiable prediction, so things didn't seem that bad as far as science goes. The company Valkee Ltd. was founded as a spin-off to manufacture the devices. Preliminary studies even tentatively indicated that in patients with SAD, there were antidepressant and anxiolytic effects. However, the studies lacked proper controls and there was no dose response. Other studies, however, showed that there were no actual physiological or psychological effects: melatonin levels were unchanged, subjective sleepiness was not reduced and performance was not improved. Further studies by the original group showed no effect on melatonin or cortisol. The proponents of the therapy tried to pooh-pooh this fact away by speculating that the effect could be mediated by the human flavoprotein CRY; there is no evidence whatsoever for this claim.

Given their simple construction — a LED and a battery — the devices are rather expensive, costing 199 €. Continuing the sale of an ineffective medical device has been criticized as unethical, and has been called out as a scam.

Valkee Ltd. filed for bankruptcy in 2021. Embarrassingly, the largest creditor was the government agency Business Finland, which had granted 1.2 M€ worth of loans to Valkee for technology development and research.