The AIP Paleo approach was developed by Sarah Ballantyne PhD out of the standard Paleo diet, as a way to manage her autoimmune issues.
This diet emphasizes removal of any chemicals additives and packaged foods for real, high quality (grassfed) animal products. The initial 30 days of the AIP is the hardest elimination diet as it eliminates grains, dairy, eggs, legumes, nightshade vegetables, nuts and seeds and the spices that comes from seeds.
As Sarah Ballantyne says in her book The Paleo Approach, after a while a person can experiment with adding in the eliminated foods to see if they can tolerate them.
Certain foods are never allowed such as grains and legumes. Some Paleo folks do eat some dairy but not on the AIP protocol.
From Dr. Ballantyne:
From Alt-Autoimmune LLC (Angie Alt)