Propionibacterium acnes is the most common pathogen identified from a surgical site infection in the shoulder. Standard skin preps do not prevent this type of infection. Patients will undergo either a chlorhexidine or benzoyl peroxide prep in days leading up to surgery. Bacterial burden will be determined at the time of surgery.

After surgical posting, patients will be randomized to chlorhexidine or benzoyl peroxide group. The solutions used will be 5% benzoyl peroxide emollient foam and 4% chlorhexidine gluconate skin cleanser. Participants will be instructed to conduct skin wash using the appropriate solution in the shower over the operative shoulder and axilla for three mornings prior to surgery (pre op day -2, pre op day -1, and morning of surgery). Specific instructions will include leaving the solution on the skin for three minutes and avoiding contact with eyes, ears, and mouth. Proper technique will be demonstrated at time of patient recruitment and given as a handout with the wash solution provided. A reminder phone call will occur two days before surgery to remind patients of proper procedure to improve compliance. On the day of surgery, patients be interviewed about pre-operative compliance.

On the day of surgery, two cultures will be taken in three separate sites on both shoulders (anterior, lateral, and posterior) using a detergent scrub technique, the current dermatologic standard for biopsy of the deep sebaceous glands. (3,11) This procedure is typically performed on the skin of awake patients and causes minimal pain and skin irritation. Cultures will be evaluated in our lab. We will also test for hemolysis as a possible indicator of a more virulent strain in the literature.

The research team may take photos of the shoulder skin being swabbed. Photos will not include the facial or defining characteristics. Photos may be taken either in the clinic at time of recruitment or in the operating room when samples are being taken.

Inclusion criteria: all patients undergoing open shoulder surgery or shoulder arthroscopy. Exclusion criteria: anyone with a history of allergic reaction to chlorhexidine or benzoyl peroxide. Anyone with a history of previous shoulder infection, current open skin lesions around the shoulder or the use of current anti-acne medications around the shoulder.

Healthy volunteer portion: Healthy volunteers will respond to the study from fliers on campus. A cotton swab test on both shoulders will be performed prior to any treatment. If a threshold of P. Acnes is met (>1000 Colony Forming Units (CFUs)) then volunteers will be randomized to the same two groups and retested after three days of unilateral treatment. Finally, volunteers will undergo repeat cotton swab testing one week after 3 day wash was finalized.

Inclusion Criteria:

• Age >18
• Indicated for shoulder surgery

Exclusion Criteria:

• History of previous shoulder infection
• Allergy to Chlorhexidine or benzoyl peroxide
• Current use of anti-acne medicine around the shoulder
• Patient is pregnant or concerned about pregnancy

1 year