LPT: Many budget, and other common brands, use undisclosed fiberglass in their memory foam mattresses.
Many budget, and other common brands, use fiberglass in their memory foam mattresses. It's used to meet fire safety compliances, but is not required to be disclosed by any regulations.
It is a huge hazard, and safety risk if the fibers ever get out, either by washing or aging. Any type of agitation to the mattress could send the fibers into the air, and stuck to your clothes. The contamination can be as bad a bed bugs, and spreads very easily between fabrics.
It can cause inflammation in your lungs, and severe irritation of your skin.
Please double check about whether your brand might have fiberglass, and consider getting another brand or a fully zippered hypoallergenic mattress protector.