Many people with autism are also hypersensitive or under-sensitive to light, noise, and touch. They may be unable to stand the sound of a dishwasher, or, on the other extreme, need to flap and even injure themselves to be fully aware of their bodies. These sensory differences are sometimes called "sensory processing disorder" or "sensory processing dysfunction," and they may be treatable with sensory integration therapy.
Sensory integration therapy is essentially a form of occupational therapy, and it is generally offered by specially trained occupational therapists. It involves specific sensory activities (swinging, bouncing, brushing, and more) that are intended to help the patient regulate his or her sensory response. The outcome of these activities may be better focus, improved behavior, and even lowered anxiety.
Because it has become a bit of a fad, however, many well-meaning occupational therapists have learned just a little about sensory integration therapy, and may be doing a poor job of implementing the approach. While this is unlikely to do a child any particular harm, it's unlikely to help much - and if a parent is paying for private therapy, it can be a very expensive mistake.
It's important to know that sensory processing disorder is NOT an official diagnosis, and there is disagreement as to whether sensory integration therapy is actually effective. While there are plenty of anecdotal stories about the success of sensory integration therapy - and research studies that support those stories - there are also plenty of studies which dispute their findings.