Hi Derek, 
 
Thanks for your question. 
 
All mattresses are prone to the issues you mention. Foam is less suceptible as they can't live in the fibres but they can live in the covers. 
 
You might want to invest in a Mattress Encasement from a company such as Allersafe online. The encasement will zip around the entire mattress and help to reduce this. 
 
Open coil springs are a continuous spring system, interconnected that create extra movement. Please see the article here for further information. 
 
I hope this helps but if you have any further queries please don't hesitate to contact our office on 0161 437 4419.
 
Kind Regards, Lee.