The purpose of this study is to investigate how pretreatment with a topical medication for acne affects application and delivery of gold microparticles to the skin in acne patients. In addition, the investigators want to investigate the biodistribution of gold microparticles in pretreated skin and compare this with the biodistribution of untreated skin using the non-invasive imaging techniques optical coherence tomography and reflectance confocal microscopy

Epiduo is a prescription gel that combines adapalene and benzoyl peroxide, two active substances for the external treatment of acne. Adapalene is a substance that resembles A-vitamin acid, which dissolves and prevents clog formation in the sebaceous glands. Benzoyl peroxide works by reducing the amount of bacteria while dissolving the clogs in the sebaceous glands. Epiduo is the only antibiotic-free combination for the treatment of acne.

Reflectance Confocal Microscopy (RCM) and Optical Coherence Tomography (OCT) are non-invasive imaging technologies allowing for imaging of the upper skin layers. Gold microparticles have been shown to have a contrast effect on the images. In addition to the contrast effect on images, gold microparticles have proven to be effective in the treatment of skin disease acne. The treatment with gold microparticles uses a combination of the gold microparticles and a laser. The microparticles consist of very small particles of silica, surrounded by a shell of gold. These two components of the microparticles are selected from their way of absorbing light from a laser. The particles absorb the light from the laser and are thus heated. The surrounding skin can not absorb the light and therefore will maintain its normal temperature.

Inclusion Criteria:

1. Patients with a clinical diagnosis of acne vulgaris, IGA score 1-3
2. 18-45 years of age at baseline
3. Legally competent, able to give verbal and written consent
4. Communicate in Danish verbally as well as in writing
5. Fitzpatrick skin phototype I-III
6. Subjects in good general health, willing to participate and able to give informed consent, and can comply with protocol requirements
7. Female subjects of childbearing potential (1) must be confirmed not pregnant by a negative urine pregnancy test prior to trial treatment
8. Female subjects must use one of following contraceptive techniques to be included in the study: intrauterine device (IUD) or hormonal contraception (birth control pills, birth control patch, birth control vaginal ring, birth control shot or birth control implant) (1) Female subjects are considered of childbearing potential unless they have been hysterectomized

Exclusion Criteria:

1. Subjects with a known allergy to gold microparticles or Epiduo®
2. Individuals with other skin disease than acne or skin lesions in the area of research interest
3. Subjects with tattoo in the treatment area which may interfere with or confound evaluation of the study
4. Subjects with moderate-severe to severe acne (IGA 4-5 and those presenting with either cysts or nodules) requiring continuation of systemic treatment during the study period
5. Subjects with a history of keloids which is deemed clinically relevant in the opinion of the investigator
6. Subjects with active skin disease or excessive scarring that, in the opinion of the investigator, would impact the ability to administer the gold microparticles or use of OCT/RCM in the areas
7. Pregnant and lactating women
8. Subjects who have received investigational drugs or were treated with investigational devices within 30 days prior to baseline
9. Treatment with oral retinoid 3 months prior to baseline
10. Treatment with systemic antibiotics 4 weeks prior to baseline
11. Topical retinoids, topical antibiotics or topical products with benzoyl peroxide 4 weeks prior to baseline