No. There should not be ill effects by Shiatsu treatment. Classic books of Oriental Medicine introduce some examples of ill effects, however, we have never heard of any cases of ill effects by Shiatsu treatment in fact. If anything bad happen during Shiatsu treatment, it will be "an accident" because of carelessness by the Shiatsu practitioner. But it must be come out from a certain cause, and the patient will realize the reason which reminds him/her of an incident during the session. Usually, in Shiatsu therapy, there is no case what Shiatsu itself produces ill effects to make abnormal symptoms whenever the therapist does Shiatsu properly and the patient receive the treatment at comfortable.