Psoriasis Microbiome and Phototherapy

Inclusion Criteria: 1. Males and females 18 years of age and older. 2. Clinical diagnosis of psoriasis for at least 6 months as determined by subject interview of his/her medical history and confirmation of diagnosis through physical examination by Investigator. 3. Stable plaque psoriasis for at least 2 months before Screening and at Baseline (Week 1) as determined by subject interview of his/her medical history. 4. Subject is a candidate for phototherapy. 5. Subject has at least one psoriatic plaque measuring at least 6cm x 2cm located on either the arms or the legs (excluding intertriginous areas such as the axilla and inguinal folds) 6. Able and willing to give written informed consent and to comply with requirements of this study protocol. Exclusion Criteria: 1. Subject has photosensitizing condition or other contraindication to phototherapy 2. Diagnosis of erythrodermic psoriasis, generalized or localized pustular psoriasis, medication-induced or medication-exacerbated psoriasis, or new onset guttate psoriasis. 3. Cannot discontinue or avoid topical therapies for psoriasis for at least 14 days prior to the Baseline (Week 1) visit and during the study other than on face, underarms, or groin. 4. Cannot discontinue or avoid UVB phototherapy or Excimer laser for at least 14 days prior to the Baseline (Week 1) visit. 5. Subject is receiving therapy for psoriasis that requires a wash out period of more than 14 days (e.g., psoralen-UVA phototherapy, oral systemic therapy, biologic therapy, or other investigational therapy). 6. Other active inflammatory dermatologic conditions (e.g., eczema) or presence of pustular or erythrodermic psoriasis. 7. Any history of acute or chronic bacterial, fungal, or viral infection (including HIV, hepatitis, tuberculosis, or other severe or recurrent infections) within 30 days of baseline sample collection. 8. Subject has used systemic (oral or parenteral) antibiotic, antimycotic, or antiviral within 3 months or topical antibiotic, antimycotic, or antiviral within 14 days of baseline sample collection or requires use of any topical or systemic antibiotic, antimycotic, or antiviral during the study. 9. Consumption of large doses of commercial probiotics (greater than or equal to 108 cfu or organisms per day) including tablets, capsules, lozenges, chewing gum or powders in which probiotic is a primary component. Ordinary dietary components such as fermented beverages/milks, yogurts, and foods do not apply. 10. Presence of comorbid medical condition (e.g., HIV, malignancy within past 5 years other than successfully treated basal cell carcinoma, non-metastatic cutaneous squamous cell carcinoma or cervical carcinoma in-situ) that significantly alters the immune system or results in immunosuppression. 11. Subject is taking (within up to 180 days of baseline sample collection) or requires topical or systemic therapy during the study that significantly alters the immune system or results in immunosuppression (e.g., chemotherapy, oral or injectable corticosteroid). Inhaled corticosteroids for stable medical conditions are allowed. 12. Unstable dietary history as defined by major changes in diet within 30 days of baseline or during study, where the subject has or plans to eliminate or significantly increase major food group in the diet. 13. Recent history of substance abuse or psychiatric illness that could preclude compliance with the protocol. 14. History of any substance abuse within 365 days of screening visit. 15. Female subject who is pregnant or breast-feeding or considering becoming pregnant during the study. 16. Major surgery of the gastrointestinal tract, with the exception of cholecystectomy and appendectomy, in the past 5 years. Any major bowel resection at any time. 17. History of active uncontrolled gastrointestinal disorders or diseases including: * Inflammatory bowel disease including ulcerative colitis, Crohn's disease, or indeterminate colitis; * Irritable bowel syndrome; * Persistent, infectious gastroenteritis, colitis, or gastritis, persistent or chronic diarrhea or unknown etiology, Clostridium difficile infection (recurrent) or Helicobacter pylori infection (untreated).