The goal of the present study is to assess the safety of a topical probiotic (probiotic strain; SS-POR11) on acne prone-skin, and the impact of SS-POR11 on the distribution of porphyrins, in subjects with mild-to-moderate acne [Investigator's Global Assessment (IGA) 1-3].

Inclusion Criteria:

• Participant's first language of French or English, given the written language of the ICF
• Participants willing to sign the ICF upon entering the study
• Participant must be willing and able (in the PI's opinion) to comply with all study requirements
• Participant must be aged 18-40 years
• Participant must have a screening and baseline IGA score of 1 (rare blemishes/clear skin) or 2-3 (mild to moderate facial acne vulgaris)
• Participant must agree to appear on all evaluation days and conform to all study-related instructions
• Participant must agree not to undergo any topical treatments in the areas under investigation during the study period

Exclusion Criteria:

• Participants under the age of 18 years or over the age of 40
• Refusal to sign the ICF
• Participants has any injuries or tumors in the areas under investigation
• Participant has a recent (i.e., 3 months) surgery or invasive treatment in the areas under investigation
• Use of oral antibiotics within 4 weeks prior to start of study
• Use of oral or topical "probiotic" products within one month prior to start of study
• Prior (3 months) or planned use of chemical peels, microdermabrasion, microneedling, or exfoliants during the course of the study
• Participant is using or has used within 3 months drugs such as corticosteroids, immunosuppressants, or others collagen-production inhibitors
• Participant is pregnant or lactating or wishes to get pregnant within the next 3 months, or refuses to use appropriate contraceptive method (in case of women of childbearing potential)
• Participant has active herpes simplex in the investigated areas or a history of herpes labialis with four or more outbreaks in the 12 months prior to baseline
• Participant has immunocompromising diseases; any known allergy or hypersensitivity to any of the ingredients of the investigational product
• Participants possessing any of the contraindications for use of SS-POR11
• Participant has tattoos, piercings, excessive scarring (e.g., hypertrophic or keloid scars) in the areas under investigation
• Current or prior (3 months) change in the use of retinoids; Initiated use of hormones or change in dose of hormonal replacement therapy within 3 months; and any other criteria that at the discretion of the Investigator, could interfere with study assessments or expose the subject to undue risk by study participation.