I'll second photomc's suggestion. I've kept all my filmholders, 4x5 and 8x10, in Ziplocs since I started doing photography in remote areas of the SW. It helps keep them clean, helps prevent the problem that you're experiencing and, as suggested, helps keep info about each holder and its data. In addition, I keep my holders in an appropriately sized cooler to help limit temp fluctuations and help keep them clean. I had a local printing company print cards on hard card stock in a size that will fit with each holder in its ziploc that has info about when the holder was loaded with what film etc.