Because oral probiotics reported to potentially induce endogenous Oxytocin, and Oxytocin has been reported to improve social behaviors, the investigators will conduct a pilot trial to compare the effects of probiotics and Oxytocin on social behavioral changes in ASD children. Additionally, the investigators will check oxytocin levels, and perform brain fMRI in some subjects, in order to determine which treatment is more efficient, sustainable, and practical, and whether both treatments in combination are better than either treatment alone. If the trial is conclusive, the investigators will conduct a trial in large scale to understand more the mechanism of ASD behaviors and corresponding effective interventions.

This study description is in accordance with the Consolidated Standards of Reporting Trials (CONSORT) guidelines that are published for the evaluation of randomized controlled trials. This clinical trial is a randomized, double-blind placebo controlled study. Subjects will be randomized to 2 groups:

Phase 1: a. oral placebo, and b. oral probiotics; Phase 2: a. intranasal Oxytocin(OXT) + oral placebo, and b. intranasal OXT + oral probiotics

The treatment will proceed for a total of 28 weeks. In the first phase (16 weeks), all the patients will be randomly and proportionally divided into two groups: Group A (30 subjects) receives oral probiotics while Group B (30 subjects) receives an oral placebo. In the second phase, subjects in Group A and Group B will continue their respective oral probiotics or placebo administration as in Phase 1. In addition, both groups will be simultaneously administered with intranasal OXT spray.

Testing will be performed 3 times total (before, during, and after treatment). The tests include behavioral surveys, cognitive tests, clinical autonomic tests, and blood tests for oxytocin levels. Investigators plan to select up to 10 subjects from each group to conduct a series of MRI studies at week 0, week 16 and week 28.

Inclusion Criteria:

1. Age between 3-25years old;
2. Pre-existing diagnosis of autism; subjects may be asked to provide documentation confirming diagnosis by DSM-V-TR criteria, ADOS, ADI-R, or other clinical forms
3. A care provider who can reliably bring the participant to study visits;
4. No planned changes in medications or psychosocial interventions during trial (stable medications within the last 2 weeks);
5. Willingness to provide blood samples

Exclusion Criteria:

1. Pregnant woman (before or during the study).
2. Comorbidity of other neurological and/or psychiatric disorders such as unstable seizures, schizophrenia, schizoaffective disorder, bipolar disorders or history of substance abuse.
3. Psychotropic medication use
4. Subjects with active cardiovascular disease that is not controlled by medication.
5. Oxytocin, antibiotic, or probiotic use within the last 30 days.
6. Regular nasal obstruction or nosebleeds
7. Significant hearing, vision, or motor impairments
8. Habitual consumption of large volumes of water
9. Started taking new medications within the last 2 weeks

There is no plan to share data with researchers not involved in this study.

this study will be double blinded for both participants/guardians and medication administrator