A specific protein (antigen) given orally is a known method of introducing tolerance of immunological response to this antigen. This method has recently been reviewed by some authors as a possible tool in the treatment of autoaggressive diseases, such as multiple sclerosis. The experimental allergic encephalomyelitis (EAE) respected animal model for MS was used for the study. The aim of the study was the evaluation of the effect of pig spinal cord protein hydrolysate given orally upon the ultrastructural changes in the blood-brain barrier image in EAE. Changes of EAE are as follows: opened channels from basal membrane (tight junction) on the border with astrocytes, fragments of organelles of the cells, oedema of astrocytes, presence of vesicles with fluid, presence of macrophages with phagolysosomes. After pre-treatment with spinal cord hydrolysate up to 6 weeks all the above changes were normalised. These findings are promising as a possible tool in the clinical treatment of sclerosis multiplex.