Collembola or "Springtails" are a common group of bugs - they're technically not insects although much like them - found all over the world.
There's no evidence that these critters are parasites for humans - except for one strange scientific report claiming to have found Collembola body parts in skin scrapings from people diagnosed with delusional parasitosis - a psychiatric disorder characterised by the belief that one is infested with parasites.
According to said 2004 paper by Altschuler et al, these patients are not delusional after all. This paper has been popular in the delusional parasitosis community.
However, insect expert Matan Shelomi says that Altschuler et al's best photo of the so-called Springtails was probably Photoshopped. He explains that in the only pic to clearly show anything resembling a 'bug' (there were many others, but none look convincing), the raw microscope image shows nothing but a blurry blob.
Altschuler et al claimed to have enhanced the contrast, but when Matan did that, there was still no visible critter. However, in the published image, a rather sinister bug is clearly seen. How did it get there?
Either the image contrast was somehow selectively enhanced just for the 'bug' part - which, of course, presumes that the bug was there, and is quite invalid - or more likely,
The level of detail present in Altschuler et al.’s enhanced image, particularly in the areas of the legs and a very odd pair of stripes along the abdomen, does not appear when contrast is applied equally. Such detail, however, can easily be created using functions such as Burn, Dodge, and Colorize on Photoshop®,when applied to select portions of the image manually as if via paintbrush.
However, Shelomi says, even if such fraud is proven, there may be nothing anyone can do: the journal the original paper was published in has since folded, so it would be impossible to retract it, and the author runs an independent non-profit and is hence not subject to scientific misconduct regulations.
Thanks very much to @benmeg for sending me a copy of this paper.
Shelomi M (2012). Evidence of Photo Manipulation in a Delusional Parasitosis Paper. The Journal of parasitology PMID: 23198757