I tend to have allergies to a lot of things. Dust, cats, dogs, and especially synthetic stuff like plastic foam or new paint. Luckily for my profession as an agronomist, I don't get allergies when I'm outside, just in houses and buildings.
As a result of my sensitivity to synthetic substances, I try to avoid using synthetic clothes, synthetic filling for pillows, synthetic paints, composite wood materials, etc. I even had my baby's crib mattress hand-made with a cotton liner and cotton stuffing. That said, I have a negative reflex against the type of people who are always talking about how toxic and horrid all consumer products are.
A few months ago my wife and I indulged ourselves and bought a new mattress for our bed. The old mattress had been stuffed with a mishmash of recycled polyurethane foam of indeterminate origin. Who knows how much toxic gas it seeped off, or how many little molds and mites were living in that thing (for that matter, how many bodily fluids of its previous users were still in there!). Either way, it gave me awful allergies, in addition to the fact that after a year of use it had gotten all smashed down and compacted, such that we were practically sleeping directly on the boards of the bedframe (people don't use box springs here in Colombia). Granted, that double mattress was a step up from the tiny single bed my wife and I had shared for most of our life together, but it was far from ideal.
So we splurged like $400US on a new mattress, complete with actual firm springs inside. We scouted our options at a few places, but settled on one from the mattress store directly underneath our apartment. The delivery consisted in carrying it up one flight of stairs!
Every mattress we saw, including the one we eventually bought, bragged that they contained "special treatments" against mites and fungi, so as to prevent allergies. I'm sure that mites and fungi give me allergies, but so do the chemicals, plus the latter have long-term toxic effects. The treatments had cheery-sounding trade names that didn't allow for easy identification of the actual chemicals involved, but after a fair amount of internet research I found that our new mattress was impregnated with a mix of pyrethrin insecticide and some basic organic fungicide. Both relatively mild as far as agrochemicals go, but nothing I wanted to be sleeping directly on top of, breathing in every night. And I certainly didn't want my pregnant wife undergoing nightly neurotoxin aromatherapy.
I believe that in places like the US and other countries with a sizeable minority of eco-conscious, wealthy consumers, it is possible to obtain mattresses without chemical treatments, but here in Colombia, at least in our small town, that was not an option. So we went with the mattress we liked, and had a thick cotton canvas cover made to sheath the mattress in. This was a piece of advice I'd taken from a handy website from a Canadian organization, offering less toxic alternatives to common products. The canvas cover more or less traps the toxic fumes inside, while also preventing the problem the chemical treatments are meant to address: allergy-inducing dust mites. With a thick mattress cover, dust mites can't get into the mattress, or if they do, they can't come out to bother you.
As with many of my more extreme schemes for sustainable living, my wife felt that the whole routine of making the canvas covers for the mattress and our pillows was a bit excessive. Even I was sure I was probably doing overkill. But a few days ago, after a particularly prodigious piss on the bed from our son Sam, I washed the mattress cover, and we have spent the past two nights sleeping without it as it dries on the line (we've had overcast, humid weather these days). The first night my nose started running as soon as we lied down, and I ended up waking up at 4am, tortured by my allergies. Last night wasn't so bad, but it wasn't great either. I'll be very happy to get that cover back on the mattress tonight.
Anyway, the moral of the story is that I now have some firsthand anecdotal evidence that the toxins in many mattresses really do exist in high enough doses to be noticeable. Do like I did, and cover your mattress up today!
Also on the general topic of less-toxic alternatives for common consumer products, here's a Spanish expose on different options for green baby care.