Photobiomodulation therapy (PBMT) is based on exposing biological tissues to low-intensity light, with effects depending on the light-tissue interaction. When irradiated without skin contact, part of the incident light is reflected and lost. In this context, the amount of reflected light in PBMT applied without skin contact, as well as the influence of skin phototype, has not yet been established. Objective: To quantify the reflection of light from PBMT on the skin of men and women aged 18 to 30 years, considering skin phototypes. Methodology: Participants will be divided into three groups based on skin phototype (Group 1: phototypes I and II; Group 2: phototypes III and IV; Group 3: phototypes V and VI) and sex. They will be subjected to whole-body PBMT with red light (660 nm; 31.85±3.85 mW; 45.50±5.07 mW/cm²) and infrared light (850 nm; 25.29±2.99 mW; 36.13±4.27 mW/cm²) at 20 cm from the light-emitting source, with measurement of light reflection in the regions of the brachial biceps, abdomen, lumbar, anterior and posterior thigh, and calf using a power and energy analyzer (powermeter PM100D and sensor S130C, 0.7 cm²). Data will be analyzed for normality and groups were compared with a significance level of 5%

Inclusion Criteria:

• male and female
• age between 18 and 30 years
• body mass index (BMI) between 18.5 and 29.9 kg/m2.

Exclusion Criteria:

• tattoo in the light reflection assessment areas
• history of skin cancer
• skin lesions such as open wounds in the mid-thigh, abdomen, biceps brachii, back and calf
• patients with cognitive difficulty reporting thermal sensation