Form plywood - how to treat sawn edges?

[vojma]

I have built a packing crate from form plywood for my snowmobile sled. I was meticulous as hell when building it and equally proud when it was finished. However, I now notice that the plywood has swollen a bit at the edges where I have open cut surfaces.

What should I treat these with to prevent swelling?

 

[Immobil]

The edges are brushed a couple of times with oil paint.