Whilst this isn't directly CH specific as the research is related to migraine, there is a good chance that the research will also apply to people with CH who get light sensitivity during a CH or shadows.

Research from Harvard medical school has found that for people with migraines who are exposed to a certain wavelength of green light there is a reduction in light sensitivity and a reduction in headache severity.

Work is being done to develop light bulbs that give out low intensity green light plus to create affordable sunglasses that block all but the required green light. It could be that "going green" is a way to make headaches less severe.

You can read about it at:

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Thank you AussieBrian for the heads up on this.

I have used a light & sound machine(Kasina) for a few years. I find low intensity green and blue light make my CH's worse. These are usually relaxation programs.

I find high intensity red light(which looks like staring into the sun) and high frequency binaural beats ease the headache, but don't usually stop them. These are "wake the brain up" type of programs.

I'll have to set up a program that uses only green light(LED) and see if it makes a difference.

Thanks for the links.