Hi amd20x6,
While I am not a fan of solid foundations unless it is a “necessary” choice that makes the tradeoff worth it such as those who want an adjustable bed, there are conflicting opinions about this issue and a solid foundation wouldn’t “guarantee” mold or other issues connected to lack of ventilation. It would really depend on several variables coming together and on your “risk tolerance” for the possibility of mold, mildew, and dust mites. You can read a little more in post #10 here.
I think that allergies to coir would be more likely for those who are involved in its production which produces a large amount of dust which can produce nasal bronchial allergies or astha with longer term exposure (see this article) but I tend to doubt that it would be likely to cause allergies with the product used in a mattress that had been cleaned and rubberized … although it’s of course possible that an allergy could occur. I would also think that it could help one of the more common allergies which is to dust mites because the greater ventilation could help reduce dust mite populations.
I just thought I would put the issues in some perspective so that it was more clear that it isn’t really a
“black and white” issue but more a matter of where in a range of risk you may be and that there is no real consensus among “experts” (although I think the majority would lean towards greater ventilation when possible).
Phoenix