What is overexposure in the use of red light therapy and why can it not be overexposed?
As a non-invasive photobiomodulation technique, the efficacy of red light therapy is closely related to the irradiation dose. The so-called "overexposure" refers to improper operations that exceed 30 minutes of single use or violate the "interval period" principle (such as continuous daily use). There are two main reasons why this phenomenon needs to be avoided. ：
- Bidirectional dose-response at the cellular level
When exposed to appropriate doses of red and near-infrared light, mitochondrial cytochrome C oxidase can be activated, promoting ATP energy synthesis. But beyond the threshold, it can actually induce excessive production of reactive oxygen species (ROS). A study published in the 2016 Nature journal showed that 30 minutes of irradiation increased ATP levels in skin fibroblasts by 47%, while the 60 minute irradiation group saw ATP levels fall below baseline, confirming the paradox of 'more ≠ better'.
- Compensation imbalance of physiological system
The human body's response to light stimuli follows biological rhythms. Continuous daily exposure can lead to:
1) The desensitization of light receptor proteins leads to a gradual decrease in therapeutic efficacy;
2) The physiological cycle of collagen synthesis and inflammation regulation is disrupted.
Just as muscle training requires rest days, NASA's clinical trials have shown that the group using red light therapy the next day had a 22% faster wound healing rate than the group using it daily.
Three typical risk cases:
- Beauty field: Temporary dehydration of the stratum corneum occurs in individuals who have been exposed to 40 minutes of radiation every day for two consecutive weeks;
- Pain management: Local tingling sensation (changes in nerve sensitivity) reported by lumbar spine patients after overuse;
- Special populations: individuals with thyroid dysfunction may interfere with hormone secretion rhythms.
The current general safety guidelines of the International Association of Optometrists (WALT) recommend:
Facial/small body parts: 10-20 minutes/time;
Large area (back/abdomen): ≤ 30 minutes/time
Must be spaced at least 48 hours apart.
Mastering the precise dosage principle of 'less is more' is essential for making red light therapy both safe and effective.
