Low-level light therapy system with an electrically passive, article of apparel that absorbs an incident spectrum including one or more of a UV wavelength, a visible wavelength, and a near infrared wavelength and emits light having an emission spectrum including visible light radiation and near infrared radiation. Light is emitted from the yarns and a textile material consisting of a network of yarns (as well as the article of apparel made from such a textile material) having an emission spectrum including visible light radiation and near infrared radiation in a direction toward a body of a person. An article of apparel that emits light in the visible/near infrared spectrum, a method of manufacture, and a low-level light therapy method are also disclosed.