I have been doing immunofluorescence on paraffin embedded slides and found that there are many blobs and dirt, regardless how many times I wash the slides. They are already there even just after dewaxing with Xylene substitute (Sigma). These obstructive blobs overflow to all channels (DAPI, FITC, Cy5, etc.) which severely affect the interpretation. Has anyone seen this kind of problem and if so how did you get rid of it?

Thanks,

Anthony