I helped build some Ikea bookshelves. I was coughing a lot when we put the first one together. Didn't think anything of it though my sister mentioned it afterwards.
Next week we got some more Ikea bookshelves in. I was coughing again after the pack was open. It's those particles.
You cut MDF in a ventilated area but assembling LDF should be much safer. There ought to be something in the instructions about ventilation. Surprised me it was that bad.