Photodynamic therapy (PDT) is considered an effective treatment for acne vulgaris. The study aims to determine whether treatment with daylight as an illumination source is as effective as conventional, red light illumination.

15 patients with acne vulgaris received 4 treatment sessions at three-week intervals. First, 5-aminolevulinic acid (ALA) was applied to the entire face. Then the face was divided into two symmetrical contralateral treatment areas: the left was covered with a light-impermeable dressing, while the right face was exposed to sunlight. After 2 hours outdoors, the right side of the face was covered, and the left half was illuminated with red light.

Photodynamic therapy (PDT) is considered an effective treatment for acne vulgaris .One of the most important drawbacks of PDT is the pain during illumination.

It has been shown that daylight PDT is an effective treatment for actinic keratosis. In order to examine the efficacy of daylight PDT for acne vulgaris, we used a split-face design: the face was divided into two symmetrical contralateral treatment areas: the left was covered with a light-impermeable dressing, while the right face was exposed to daylight. After 2 hours outdoors, the right side of the face was covered, and the left half was illuminated with red light.

Inclusion Criteria:

• Patients with a clinical diagnosis of acne vulgaris on the face
• Acne lesions include inflammatory papules/ pustules/ nodules and cysts , and non-inflammatory open and closed comedones.
• Acne refractory to conventional therapies
• Patients who are unable or do not want to take oral isotretinoin
• Patients who cannot tolerate isotretinoin

Exclusion Criteria:

• History of oral retinoid use within 12 months of study entry
• Systemic antibiotics within 6 month of study entry
• Topical acne treatment within 1 month of study entry
• Presence of any other skin disease that could interfere with the assessment of the acne, such as folliculitis or rosacea
• Presence of any other systemic disease that could affect the acne severity by its presence, such as polycystic ovarian syndrome, or by any medication prescribed for the treatment of the systemic diseases (retinoids, antibiotics).
• Pregnancy or intention to get pregnant
• lactating woman
• Porphyria
• Photosensitive dermatoses
• Allergy to any component of the photosensitizer compound
• Personal history of melanoma or dysplastic nevi
• A beard or other facial hair that might interfere with study assessments;

The photographs of the patients were evaluated by two dermatologists blinded to the study protocol.