I have always understood /r/trypophobia to be a deep in-joke, and the earliest i can find reference to the idea at all is 2005: https://web.archive.org/web/20090316071914/http://www.geocit...
and that smells tongue-in-cheek too.
But yes, it's a weird, weird thing. No one ever talked about being afraid of clowns when I was a kid. Lots of people liked them, lots were indifferent, but I don't recall ever hearing anyone say they were frightened of them until much later in life. And I clearly remember the first time I heard of anyone disliking the word "moist", and thinking I was being trolled.
My second early incident was seeing the cover of the O'Reilly book "Windows Annoyances", which features an image of a Surinam toad with young embedded on its back. Yes, I wasn't a fan of Windows at the time, but I couldn't imagine what the editors were thinking when they chose that cover image.
I personally had physical reactions of disgust and an unusual desire to destroy Lotus seed pods the first time I saw them. I wanted to put them on the cement and smash and grind them with my shoe until they were a fine paste. This was before I had ever heard the word "trypophobia".
The only thing in nature I've found to trigger me is Lotus seed pods. Unlike your example of the doctored images, there is nothing objectively gross about seed pods, they are a natural part of a healthy and harmless plant.
Call it morbid curiosity, but I will sometimes browse /r/trypophobia and I get the same feelings there, but never worse than simply viewing a seed pod.
Should've read the rest of your comment before googling that. I didn't expect as strong a reaction as I just had upon seeing those. Deeply unsettling.
The way I've always interpreted it is that it looks like and reminds us of an infected pimple/abscess/parasite/something growing under the skin where it shouldn't be, coupled with enough empathy or imagination to picture it happening to us. The natural reaction is then disgust and aversion. It's just a result of the way our brains are built, similar to seeing faces where they don't exist.
I'm pretty sure I've seen a lotus seed pod in real life and didn't have a reaction, since it's much easier to construct a mental image of what it really is instead of what it might be.
I also have had a history, prior to being exposed to the concept of trypophobia, of body-horror nightmares where lots of tiny holes open up in my skin around my joints, so yeah, it's probably one of those common fears.
(Google that only if you're reasonably confident you're not a tryptophobe. :) )
I wouldn't call it a phobia but I get a very real reaction from it.
more seriously though, it seems strange that a lot of things I wouldn't notice at all unless there was some really bad trigger, like photoshopped trypto images and then I start noticing this pattern more (especially if there is something sticking out of those holes...)
bee/wasp honey combs with their younglings, anybody?