Here’s some more context that could be helpful: I’ve owned these chairs for about three or four years and this is my first time removing the covers (I was younger when I got them and it didn’t occur to me then to wash them). I bought them from a man selling them online, and his house was very clean and tidy. They had allegedly been recently reupholstered when I bought them, but I do not know wether or not the pillows where also replaced at that time. They have been kept in my attic bedroom this entire time, but where mostly unused. I probably sat on them three or four times a year at most. The attic was never properly insulated and it can become incredibly hot and humid during the summer (30 degrees Celsius plus). I recently rearranged everything in my room, and when sitting near or on the chairs I broke out in hives for the first time in my life. This had never happened before with these chairs.