You have not provided any proper system information, so nobody can tell you what is going on.
Are you sure its ram and not scratch space you running low on. You give no detail as to how you determined that Photoshop is allocating all your ram. No mention of any monitor used or a printout of the resources being used by Photoshop. No machine or OS information.
I believe scratch is fine, currently running on about 100Gb free disk space. I am running OS 10.9.3, and once I open PS, my RAM is completely filled up, as you may see in Memory Used (Memória Usada). As far as I know, this shows the amount os memory that is been used, allocated or reserved by any or all application. Well, I might say it started to behave like this only after I updated to CC 2014. Before that, Memory Used gets between 5 to 10GB depending on what I was working on PS.
Even after quitting PS, my Memory Used doesn't fall far from 13GB and my overall system performance has a little slow down. The strange thing is that PS process is occupying only 142MB at this point. But its visible the diference comparing to previous version of PS.
Performance settings in PS were changed to a lower value, sitting now around 30% of free RAM. At this point I found strange that Settings inform it is 13GB available RAM, since I have 14GB installed, what amount is system using, probably not enough to run properly. I mean this looks really wrong. Or PS is not correctly displaying RAM amounts or System is not reserving enough resources to work with.
From that monitor what makes you think the problem is with RAM and its Photoshop using the RAM. Much RAM seem unaccounted for the. Bottom section seems to show. 14GB is allocated but the top details section seems only show that a few GB are in use and both Bridge and you browser is using more RAM then Photoshop I not know much about Apple other then mac's use a Unix OS. Unix is widely used but I have not run a Unix system in over 12 years.