Dysmenorrhea is the most common health problem in women in the reproductive age(Bakhsh et al., 2022). The primary dysmenorrhea starts shortly after the menarche the pain lasting 1 to 3 days that start just before or at the onset of menstruation with the absence of other gynecological symptoms (Itani et al., 2022). Primary dysmenorrhea can reduce the quality of life and social activities of women(Esan et al., 2024).

There is a relationship between body mass composition and primary dysmenorrhea and as the value of body mass index and body fat percentages goes on increasing in females, the severity of primary dysmenorrhea also increased (Wu et al., 2022).

BIOPTRON® Light therapy system is a device that contains an optical unit. This unit emits light with an electromagnetic spectrum produced by the sun, but without the ultraviolet rays and it is significant with four main characteristics which are Polarization, Polychromatic, Incoherence and low energy light (Raeissadat et al., 2014).

The Purpose of the Study The aim of the study is to investigate the effect of bioptron© light therapy on primary dysmenorrhoea outcomes as pain and quality of life among obese adolescence.

Inclusion Criteria:

• 144 female adolescences suffering from primary dysmenorrhea pain determined according to the sample size calculation adapted from (Gu et al., 2022).
• They will be selected from the outpatient's clinic of the faculty of Physical Therapy Sinai University.
• Their chronological age ranged from 16 to 18 years old.

Exclusion Criteria:

• Those who were taking anti-psychotic or anti-depressant medications, patients with any skin lesion or infection.
• Gynecological disorders included cervical cancer, ovarian tumors, endometriosis, uterine fibroids, polycystic ovarian syndrome, and other conditions that can affect menstruation.