The characters combine literally to mean “spicy eyes.” This vivid, physical metaphor was quickly adopted by Chinese netizens to describe a purely visual experience that is so bad it feels like a physical discomfort.
辣眼睛 is a product of modern Chinese internet culture. It gained widespread popularity around 2016 and has since become a staple in the vocabulary of younger generations. Its rise reflects a broader trend in online communication that favors humorous, exaggerated, and highly visual metaphors to express opinions.
This is a highly informal term. It's used constantly in casual settings, especially online.
Its connotation is almost always negative, but the tone is often light-hearted and humorous rather than genuinely hateful.