If you have looked at the availability of rolls of red and near infrared LED lights, you will see that there is a bewildering array, between orangey-red (630nm) to out of the visible spectrum so that you can't see it at all (940nm).

So what, you ask. Surely it doesn't matter? Surely red light, near infrared light - it's all the same? One wavelength is as good as another?

Wavelength matters - please be cautious!

I've been corresponding with lots of people over the last week. In my response, I always ask whether the query is for uncomplicated Parkinson's disease, or for PD complicated by another neurodegenerative process. I'm not asking because I'm being nosey - the question is really important.

I've made light hats with a range of wavelengths for people with PD and other neurodegenerative conditions over the last three years, and I have had the privilege of observing them and speaking with them and their families about their experiences.

What I have learned is this:

1. 670nm, the dark red, seemed to help everyone. Sometimes just a little, sometimes a lot.

2. If you have uncomplicated Parkinson's Disease, the best option is the use of two wavelengths, one 670nm followed immediately by 810nm.

3. If you have any other kind of disease affecting your brain cells, then you should be VERY cautious. We simply don't know enough to make any recommendations apart from 670nm.

My experience is that 810nm, 850nm and 940nm didn't seem to suit everyone, especially the more unusual neurodegenerative conditions.

If you ask me what I would make for my mother if she had straight-forward Parkinson's disease, I'd say, with confidence, use sequential 670nm and 810nm.

If you ask me what I would make for my mother if she had Parkinson's Plus or any other neurodegenerative condition, I would err on the side of caution and just use 670nm.

If in doubt, just use 670nm.