I would agree with what iiwo has said, in that milk is not a cause of Autism, but rather in SOME individuals avoidance of milk could alleviate symptoms. Milk can affect the individual in three different ways:
1. Lactose intolerance(lack of the enzyme lactase)--inability to cleave glucose from galactose, which then prevents these to simple compounds from being absorbed in the small intestine. Instead they proceed down to the large intestine where they are consumed by the microbiota, resulting in the common symptoms associated with lactose intolerance.
2. Milk Allergy--consumption of milk causes an immediate or delayed reaction. Immediate reaction would be rash, hives, itching, swelling digestive problems, etc. The delayed reactions are more difficult to pinpoint to their origin because the symptoms may occur at varying intervals and intensities.
3. Casein sensitivity--this has to do with a lack of the DPP4 peptidase enzyme(which is also found protruding from certain lymphocytes but has a different job and is called CD26), which results in a small undigested amino acid chain that bears its mischevious nature from mimickry in two ways. One way is that the immune system may react to this suspicious looking peptide, which may mimic a viral peptide thus causing a heightened immune response but no replicating virus to attack, thus evoking an autoimmune response. The second way is that in individuals that have more permeable intestinal lumens, many peptides can enter the blood stream. Whereas, in an individual without permeability problems and solid digestion of proteins, generally only has individual amino acids enter the bloodstream with the occassional larger peptide passing. The thing is that this particular uncleaved casein peptide can mimic endorphins which when unregulated can cause substantial changes in mood, behaviour and perception.
In the case of Autism I would be looking for casein sensitivity as the prime antagonist of the three.
Patriot