Below is a summary of the differences between Occupational Therapy and Physical Therapy in terms of treating children with Autism Spectrum Disorders specifically…
…Sensory Integration: Many autistic individuals have sensory problems, which can range from mild to severe. These problems involve either hypersensitivity or hyposensitivity to stimulation. Sensory integration focuses primarily on three senses–vestibular (i.e., motion, balance), tactile (i.e., touch), and proprioception (e.g., joints, ligaments). Many techniques are used to stimulate these senses in order to normalize them.
**Occupational Therapy: Can be beneficial for the sensory needs of these children, who often have hypo and/or hyper sensitivities to sound, sight, smell, touch, and taste. May include sensory integration (above).
Physical Therapy: Often children with autism have limited gross and fine motor skills, so physical therapy can be helpful. May also include sensory integration (above)**…
(source: http://www.autismtoday.com/adviceforparents.pdf )