[SkepticalDebunker (OP)]

it's a huge rage now - there's supposedly some legit studies showing what certain wavelengths can do (skin, hair, cellular reconstruction, etc) - and there's some red light beds selling into the tens of thousands of dollars.

Judging from this Forbes article it would seem that red light magically cures everything.

https://www.forbes.com/health/wellness/red-light-therapy/

There are even sources suggesting that red light can cure people's allergies.

There doesn't seem to be a plausible explanation as to why red light "activates mitochondria" or "activates cellular repair" and other colors don't. "It's because of the wavelengths" seems like a cop-out answer to me.

If the color red is so beneficial to our health then why are hospital lights still white? Shouldn't they be changing their lightbulbs to red ones to lower glucose levels, accelerate healing, bring relief from chronic illnesses and prevent obesity?

[Eternal Student]

Hi.

    Some of the phrases in that article you linked to include:

more research is necessary to fully determine its potential benefits. ;

it's important to keep in mind that many of the published studies using red light as therapy are often small (less than 30 people), animal or lab studies. As a result, most medical professionals agree that more quality research with more human participants is needed.;

They're not dramatic treatments, ;

    You should also add your own experience and assessment of Magazine or website articles.   No one wants to write an article that says "there's not much evidence here".... you can sell more if you are able to say  "there may be some effect here".
    However, some of article was interesting.    The problems of wound healing in zero-G environments and the possible use of red light was interesting and not something I was previously aware of.   Apparently this has been identified many years ago and there are quite a few articles about this already.  Here's a short one:
https://www.newscientist.com/article/mg16322053-100-space-healing/

why are hospital lights still white?

I don't know and I'm not an expert.   These reasons seem sensible:

    (i) There isn't enough evidence for the benficial effects yet.
    (ii)  You need to do more with the light than just heal surface skin injuries.  Patients want to read a book.   Older and partially sighted people want to be able to walk to the bathroom without crashing into obstacles.   Nurses want to be able to see skin rashes in a natural white light not some low intensity red light   etc.
    (iii)   Red is an inherently low-energy and hence low-intensity light.   It's not bright or easy to see with.   It's not cheerful or motivating to get up and do something - like a jigsaw puzzle in the day room etc.    Keeping patients optimistic and motivated is at least as important for getting them well as healing their minor skin complaints.
      (iv) As mentioned in your Forbes article, if you had very powerfull red light emitters all along the hospital wards, then you would also need to issue eye protection to every patient, nurse, doctor, visitor etc.

Let's also do something similar to that magazine article and close with a nugget of information:

  Did you Know?         There already is some red light in white light.   

Best Wishes.

[alancalverd]

Red light does indeed penetrate the epidermis to a greater extent than blue, but all the "red light therapy" installations I have seen (I get involved with a lot of "fringe" stuff!) also produce a fair bit of radiant heat, free coffee, and pleasant music. Plus handsome, enthusiastic, young therapists.

The UK Department of Health ran a trial back in the 1970s comparing the effectiveness of chiropractors (all private) with NHS physiotherapists doing pretty much the same thing with thousands of back pain sufferers. Chiropractors won by a country mile. So I asked one of the participants why. He said "They phone me,  talk directly to the consultant, get an appointment tomorrow, free car park, free coffee, clean toilet, no waiting for x-rays.  They feel better before I've even touched them."

You could save a bit of money by building hospitals with no windows  (less  heat loss in winter, less heat gain in summer) and equipping them with red LED lights. The dark-adapted human eye is  more sensitive to red light, which is why it is used in cockpits and ships' bridges at night. But it's difficult to discriminate blood under red illumination, which rather compromises surgery.

[Janus]

Red light does indeed penetrate the epidermis to a greater extent than blue, but all the "red light therapy" installations I have seen (I get involved with a lot of "fringe" stuff!) also produce a fair bit of radiant heat, free coffee, and pleasant music. Plus handsome, enthusiastic, young therapists.

 The dark-adapted human eye is  more sensitive to red light, which is why it is used in cockpits and ships' bridges at night.

No. It is because red light doesn't trigger the transition from night vision to day vision. Night vision uses the rods of our eyes, and they start activating due to the production of rhodopsin, which takes a good bit of time become fully effective.  It reacts with and decays rapidly when exposed to high enough levels of light.  Thus when your eyes have become dark adaptive, and you look at a bright light, this neutralizes the rhodopsin, shuts down the rods, and you lose your dark adaptation.
Rhodopsin is not sensitive to red light*, so it doesn't break down, thus preserving your dark adaptation.  The red light in ship bridges and cockpits at night is to preserve the occupants' night vision, allowing them to see outside better. 

* The photosensitive chemicals used for black and white photography are the same way, which is why you can use a red "safe-light" in a darkroom while developing.

[alancalverd]

Never too old to learn! Indeed the Purkinje effect is exactly the opposite of what I said!

[set fair]

This guy isn't a loony and neither is he selling red lights 
https://www.youtube.com/@Medcram/videos

[paul cotter]

Ever look at a coloured object illuminated solely by a low pressure sodium lamp? Ok, it is not red but close to a monochromatic orange light, close enough. It is very hard to obtain any colour discrimination. Also I could believe in some small benefit from red illumination but I reckon it would be minimal.

[alancalverd]

This guy isn't a loony and neither is he selling red lights 
https://www.youtube.com/@Medcram/videos

He does point out that atmospheric water absorbs most of the near infrared from the sun, then states that exposure to sunshine is beneficial because of the NIR. I can't help thinking that fresh air and birdsong, or just walking away from your  computer,  are a more significant part of the healing process.