Reviewed by: Dr. Alex Tam, DC
Red light therapy, also called photobiomodulation (PBM), is generally well tolerated when used with appropriate treatment parameters. Some people may notice temporary warmth, mild redness, or other short-lived changes after a session. Responses can vary depending on the device, wavelength, treatment dose, treatment area, and individual sensitivity.[1] Severe pain, blistering, significant skin changes, or symptoms that continue to worsen should be discussed with a healthcare provider.
What Side Effects Are Normal After Red Light Therapy?
Red light therapy and other forms of photobiomodulation are generally well tolerated in clinical research, although reported reactions vary by treatment parameters, device, and the condition being treated.[2]
When reactions occur, they may include:
- Temporary warmth in the treated area
- Mild redness that resolves after treatment
- Temporary skin sensitivity
- Short-term changes in how a treated area feels
- Mild irritation or discomfort in some circumstances
Clinical safety research has generally found mild, temporary reactions rather than serious adverse events when red-light treatment is delivered within studied parameters. However, higher doses or inappropriate treatment parameters can increase the risk of unwanted skin reactions, which is why treatment settings matter.[3]
How Long Do Red Light Therapy Side Effects Last?
When mild reactions occur after red light therapy, they are generally temporary. The exact duration varies depending on the treatment device, wavelength, dose, treatment area, and individual response. Research has reported temporary redness and other skin changes following some red-light treatment protocols, while more significant reactions have been associated with higher treatment doses.[4]
Immediately After Treatment
You may notice warmth or mild changes in the treated area shortly after a session. These sensations should not become progressively more severe.
Within the First 24 Hours
Mild redness or sensitivity may remain temporarily after treatment. If a reaction is becoming more intense rather than improving, contact your provider for guidance.
Over the Following Days
Most mild treatment-related changes should gradually improve. Persistent redness, significant irritation, blistering, or worsening pain should not be assumed to be a normal treatment response.
After Repeated Treatments
Your response can change as treatment continues. If a new reaction develops or an existing reaction becomes more severe after subsequent sessions, tell your provider so the treatment parameters can be reviewed.
What Happens After Your First Red Light Therapy Session?
After a first red light therapy session, some people notice warmth or temporary changes in the treated area. Others may notice no immediate physical reaction at all. Responses vary based on the treatment parameters, treatment area, individual sensitivity, and the condition being treated.
A lack of immediate symptoms does not mean the treatment was ineffective, and experiencing a temporary sensation does not necessarily indicate that treatment is working. Your provider can help you determine what to expect based on the specific therapy and treatment plan being used.
Can Red Light Therapy Make Pain Feel Worse Before It Gets Better?
Some people may notice temporary changes in pain or symptom intensity after treatment, but a clear or persistent worsening of symptoms should not automatically be considered a normal part of healing. Photobiomodulation has a dose-dependent response, and treatment effects can vary according to factors such as wavelength, fluence, irradiance, and treatment timing.[5]
If pain becomes significantly worse, continues to increase, or repeatedly worsens after treatment, contact your provider rather than assuming the reaction is part of the healing process. Your provider can determine whether the treatment dose or treatment plan should be adjusted.
Patients experiencing persistent pain may benefit from a comprehensive evaluation through our Vacaville pain management approach.
What Red Light Therapy Side Effects Mean You Should Stop Treatment?
Most mild reactions do not require emergency care, but certain symptoms should prompt you to stop treatment and contact your provider:
- Severe or worsening pain during or after a session
- Blistering or significant skin injury
- Severe or persistent skin irritation
- Symptoms that continue to worsen rather than improve
- Hives, significant swelling, or other signs of an allergic-type reaction
- A new reaction that concerns you or occurs after a change in treatment settings
Adverse reactions are not expected for most appropriately administered treatments, but the risk can vary depending on the device and treatment parameters. If you experience a significant or unexpected reaction, pause treatment and contact your provider.
Why Screening Matters Before Red Light Therapy
A brief health history before treatment can help identify situations where additional evaluation or treatment modifications may be appropriate. Screening also allows your provider to consider the specific device, treatment area, and treatment parameters being used.
People with certain photosensitivity conditions, those taking photosensitizing medications, people who are pregnant or planning pregnancy, and people with cancer-related concerns should discuss red light therapy with a qualified healthcare provider before treatment.[6]
People with implanted electronic devices should also tell their provider before treatment so the specific device and therapy can be evaluated. Safety considerations can vary depending on the treatment and device being used.
How Can You Reduce the Chance of Side Effects From Red Light Therapy?
Following the treatment parameters recommended for your specific device and condition can help reduce the risk of unwanted reactions. Before treatment, tell your provider about medications, medical conditions, previous reactions to light-based treatments, and any changes in your health history.
- Use the treatment intensity and duration recommended for your specific therapy
- Follow the recommended treatment schedule
- Tell your provider about photosensitivity or previous reactions to light-based treatments
- Report new or worsening symptoms rather than increasing treatment on your own
- Follow your provider's instructions for protecting sensitive treatment areas
Red light therapy is one component of a broader care plan for some patients. Learn more about our full-body red light therapy treatment options.
Frequently Asked Questions
References
1. Hamblin MR. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophys. 2017;4(3):337-361. PubMed
2. de Freitas LF, Hamblin MR. Proposed mechanisms of photobiomodulation or low-level light therapy. IEEE J Sel Top Quantum Electron. 2016;22(3):7000417. PubMed
3. Chung H, Dai T, Sharma SK, Huang YY, Carroll JD, Hamblin MR. The nuts and bolts of low-level laser (light) therapy. Ann Biomed Eng. 2012;40(2):516-533. PubMed
4. Glass GE. Photobiomodulation: The clinical applications of low-level light therapy. Aesthetic Surg J. 2021;41(6):723-738. PubMed
5. Huang YY, Sharma SK, Carroll J, Hamblin MR. Biphasic dose response in low level light therapy. Dose Response. 2009;7(4):358-383. PubMed
6. Haslerud S, Lopes-Martins RAB, Frigo L, et al. Low-level laser therapy and light-emitting diode therapy for pain control: a systematic review. Photomed Laser Surg. 2015;33(6):315-328. PubMed
This content has been reviewed by our healthcare professionals for accuracy and educational purposes. It should not be used as a substitute for professional medical advice, diagnosis, or treatment.
