 The use of complementary and alternative methods CAM of treatment is common and includes especially elimination diets, which are intended to minimize symptoms. The basis for the potentially beneficial impact of dietary intervention has been reported in connection to the correlation between congenital metabolic disorders phenylketonuria in patients with ASD and improvements in their overt symptoms in patients with schizophrenia Excessive activity of peptides derived from the metabolism of gluten and casein in individuals with ASD is thought to result in impaired neurotransmission in the brain. The increased permeability of the intestinal barrier, resulting from the inflammatory response the theory of leaky gut in ASD patients, simultaneously promotes excessive absorption of those compounds. Another hypothesis assumes the effectiveness of elimination diets in children with ASD, suggesting allergic background of neuropsychiatric symptoms. Additionally it is emphasized that the lack of ability to communicate symptoms or atypical clinical manifestations i.e. neuropsychiatric symptoms like hyperactivity, sleep disorders in children with ASD can make the diagnosis of gastrointestinal symptoms, allergy and other symptoms particularly difficult. Moreover the pain or discomfort may increase the risk of behavioral symptoms. 