I would think that it's because of the arachidonic acid in eggs. This is from the PP website and its also covered in the PP book.

Are there people who should avoid red meat and eggs?

Yes. Some people just seem to have a sensitivity to them. It may be the arachidonic acid found in red meat and egg yolks. These people lose weight just fine eating them, but their elevated blood pressure or cholesterol won’t come down until they stop the red meat and eggs. Sometimes people do better avoiding them if you are suffering from hypertension, elevated cholesterol, fluid retention, or inflammation such as arthritis, bursitis, asthma, allergies and rashes.

Karen