Why would a poly filter overflow skimmer

[CHEMCHEF]

I can't seem to add a poly filter or a filter sock without my skimmer going berserk for a day or two. This is very frustrating.
Filter sock will do this until it is washed like 5 times.
Tonight I added a 2"x2" piece of poly pad and I'm getting the same problem.

 

[bonomo53]

I used to have this problem with my filter socks to but now i just turn my skimmer off before i change them then wait an hour after there in to turn it back on.

 

[Will]

Just something I came across, doesn't really explain why however does say that it's normal....
I did see something else about it.... that polyfilters contain a surfactant that make skimmers go wild...Go Figure

Poly-Filter And Protein Skimmers
When putting a new PolyFilter pad into the aqaurium, there will be a tendency for the protein skimmer to foam excessively and even overflow, pulling in a lot of clear aquarium water. This is normal and is to be expected.
I usually empty out and wash the skimmer cup before I put in a new PolyFilter pad. That way, if the skimmer cup overflows, it is not returning a bunch of brown skimmate into the sump as well.
Skimmer operation should return to normal after several hours.

Also