The images were gathered from a few different communities on Reddit. First among them was /r/MildlyUncomfortable. This community of roughly 3.2k Redditors collects pictures that make you uncomfortable, but only mildly. The truly shocking and nasty images would be elsewhere on NSFW communities or other websites entirely.

Another similar reddit community is /r/mildlyunsettling. This 3.5k-strong subreddit has considerable overlap with /r/MildlyUncomfortable, but we find that the content on this one is a touch more unsettling and frightful!

The things that can make an image unsettling or uncomfortable can be quite subjective, as any quick glances at either of these online communities will show. However, there are quite a few common aspects that can make images hard to stomach.

One is the concept of the uncanny valley. Humans tend to have a well-documented discomfort with any image that makes a credible but failed attempt at appearing human. Highly abstracted imitations of human faces like emojis or cartoon characters are fine, but androids, poorly animated 3D visages, and people wearing rubber masks can all make us feel creeped out.

Another commonly cited example, only one of many visible phobias, is trypophobia. This is a fear of or discomfort with patterns of closely grouped holes. The scientific jury is still out on WHY so many of us have this reaction of disgust, but some theories suggest that this may be a hard-wired reaction to detect the scales of venomous reptiles or other dangerous creatures.