Summary
Hosts Justin and Dr. Sydnee McElroy explore the history of chromotherapy and blue light therapy, tracing its origins to Augustus James Pleasanton, a Civil War-era brigadier general who became fascinated with the healing potential of colored light. Pleasanton observed that the blue sky correlated with plant growth in spring and summer, leading him to experiment with blue-paned glass and its effects on living things, though his reasoning was a classic example of confusing correlation with causation. The episode takes a skeptical, entertaining look at how color therapy evolved from ancient Greek and Egyptian references through 19th century pseudoscience to modern light therapy applications. While the episode primarily covers the historical context of chromotherapy and Pleasanton's misguided experiments, it provides useful context for understanding how legitimate photobiomodulation research eventually emerged from a field long associated with unproven claims about colored light healing.
Key Points
- Augustus James Pleasanton, a Civil War brigadier general, pioneered the 19th century "blue glass craze" based on correlating blue sky with plant growth
- His reasoning was a classic example of correlation vs causation: blue sky appears in spring when plants grow, so blue light must make plants grow
- Ancient Greek, Egyptian, and Islamic medical traditions referenced color in healing, but chromotherapy was not established as a formal practice until the 19th century
- By the 19th century, medicine was separating from spiritual traditions, making Pleasanton's color-based healing claims somewhat revolutionary yet scientifically unfounded
- The blue glass craze led many houses from a certain period of American history to have blue panes in their windows
- The episode provides historical context for how legitimate photobiomodulation research emerged from a field long associated with pseudoscience
Key Moments
The 19th century blue glass craze and correlation vs causation
The hosts trace how Augustus James Pleasanton concluded blue light must heal because the sky is blue during spring when plants thrive, a textbook case of confusing correlation with causation that launched the blue glass craze across America.
"A.J. Pleasanton. He was born in 1808 in Washington, D.C. His dad worked in the State Department. He was also a hero. He fought in the War of 1812. And he was chief of the Lighthouse Department. A very important job. Got to keep those boats coming in safely. I just really like the idea that there was a point where we had a lighthouse department, like a whole state department. There was the lighthouse department and he was in charge of it. That seems like a really fun department to be in charge of. He's the guy at the bottom who's like yelling up like, how's it going up there? They're like, good, it's on. He's like, excellent. Keep doing it. Yeah, I know. Keep doing it. Keep it on. on, yep, thumbs up Well, we've talked about on previous episodes How important sailors were And like the shipping industry and everything So like, you gotta imagine lighthouses Were pretty darn important Important Just like proper pronunciation It's gonna be a rough one today What was the sailors thing recently Where we talked about it's the reason we have some sort of insurance or something? What was that? Well, we talked about the beginning – yes, because we talked about the hospitals that they set up. Oh, right. Yeah, yeah, yeah. I got you. How that led to the creation of the public health system and then the Surgeon General. Yes, Surgeon General. That's what it was. Okay, sorry. I'm getting distracted. I think the Coast Guard actually runs the Lighthouses now. They're in charge. Seems like a good fit. Yes, that seems like a good place for the Lighthouse Department to go. I think it was like, well, we talked about this. A lot of things that sort of shuffled around different government departments for a while. It was like in the Treasury. The treasury was like the catch-all, I believe, because they only made three, and then they threw everything they didn't know what to do with in the treasury. It was like the junk drawer of the government. And then they were like, we should make something new. Let's make a Coast Guard and put the lighthouses there. Anyway, A.J. followed his dad's footsteps. He served his country. He was in the Pennsylvania militiaia he once tried to stop some rioters in philadelphia in 1844 um i only mention this because he got shot while that was happening he does not die at this time that would be a weird that would be a weird episode anyway that's the whole bit that's it it has nothing to do with medicine no but he got shot and he forever had a musket ball in his groin. It was just there forever. Bet that made walking through metal detectors really annoying. Well, you know, in 1844, they're probably... I know they trained dogs to detect metal. I know, Sidney, I know. I don't think that's accurate. During the Civil War, he was appointed the rank of Brigadier General of the Pennsylvania Militia. And he basically worked to defend the city of Philadelphia. That was his divisions, his group, his club. That's not what it's called. My civilian-ishness is showing. I bet his dad is very judgmental. Like, oh, nice. Defending Philadelphia. Get a lot of lighthouses there? Kind of an embarrassment to me, son. There's very few lighthouses in the downtown Philadelphia. But there probably are lighthouses in Philadelphia, right? I have no way of answering that question, and neither do you. And this is the exact thinking that got us into trouble at the beginning of the episode. Well, why don't I tell you more about AJ and you really quickly Google how many lighthouses are or aren't there in Philadelphia. Thank you. After serving honorably and returning from the military, he was bored, I guess. He was in retirement. He needed a project. That happens to so many people my grandpa retired and then he started a microfilming business yeah so you know you got to have a project aj decided to get into two things he had a couple passions have you figured out the lighthouse question yet yeah they got some most notable seems to be the turtle rock lighthouse which is uh Built built in 1887 which is a little bit after his tenure there. Although maybe he was walking around Philadelphia like, God, we could use a lighthouse down here. Something in my DNA says to me, we need a lighthouse. So, I am at the point where he has left the military and he's getting into other things. So, he liked growing and farming or maybe he just had to do it out of necessity. Either way, it was something he was going to be doing. He also liked colors. Who doesn't? Much like my children. He liked colors. So, I guess it was either like he could make one of those Fisher Price little people farms because those have growing and farming and they're very colorful. Or he could do something else. If he invented that, he would have been rolling in it. He really should have. Because, well, yeah, he would have made a lot more money. Except he'd be like, anyway, they're made of plastic. And he'd be like, what are you talking about? I like the idea that he said they're made of plastic without like, I don't know what plastic is or how to make it. I just know they will be made of plastic. I'm putting the big idea out there. I've got no way to achieve it, but I'm going to put the big idea out there. Okay. Plastic was admitted in 1862. So I feel very confident in my assertion that he, that it hadn't really ramped up enough. I mean, maybe he heard about it in the, This is... Yeah. This would have been... So plastic was in existence. That is settled. It would be so new. Why do people keep asking if he made Fisher-Price Little People? He didn't, folks. He didn't. He didn't have anything to do with plastic. This is not where we're going. He was investigating the health benefits of different colors. Okay. That is the interest he had he he wanted to know specifically uh different colors of light is is where he really sort of focused color in general but like the idea of uh light filtered through different colors like panes of glass or something and the impact that could have on living things now this is before you've probably you're hearing you're hearing this and you're thinking, well, so he was interested in chromotherapy."
Ancient roots of color therapy before modern photobiomodulation
Dr. McElroy explains how chromotherapy existed in fragments throughout ancient Greek, Egyptian, and Islamic medicine, but by the 19th century medicine was separating from spiritual traditions, making Pleasanton's color-based claims both revolutionary and scientifically unfounded.
"By the 19th century, those were separating. Medicine was becoming a very empiric, well, slowly empiric thing, something in the physical world, something you could see and measure, and something quite detached from spiritual traditions."
