Inclusion Criteria:  Provide written informed consent. Must meet age criteria. Must have a diagnosis of atopic dermatitis (AD)for at least 6 months.  Must have severity of atopic dermatitis meeting the below criteria at both Screening and Day 1:  An IGA of 2, 3 or 4 on the vIGA scale, and; A BSA of ≥5%, and; An EASI score of ≥6. Must agree to use emollients. Must meet contraception requirements.  Exclusion Criteria:  Have been in a clinical trial for EDP1815 prior to signing of ICF. Use of phototherapy or tanning beds; systemic medications/treatments that could affect AD or its symptoms including immunosuppressive therapy (e.g., oral or injectable corticosteroids, methotrexate, azathioprine, cyclosporine, mycophenolate mofetil, JAK inhibitors, tacrolimus, and/or leukotriene inhibitor) within 4 weeks of randomization. Treatment with topical agents that could affect atopic dermatitis, including topical corticosteroids, topical calcineurin inhibitors (e.g., tacrolimus or pimecrolimus), or topical PDE-4 inhibitor (e.g., crisaborole) within 14 days prior to randomization. Clinically significant abnormalities in screening laboratory values that in the opinion of the Investigator would make a participant unsuitable for inclusion in the study. One retest is permitted within the 28-day screening window. Hypersensitivity to P histicola or to any of the excipients. Unwillingness to comply with study procedures, including follow-up, as specified by this protocol, or unwillingness to cooperate fully with the Investigator. Have any other conditions, which, in the opinion of the Investigator or Sponsor, would make the participant unsuitable for inclusion or could interfere with the participant participating in or completing the study.