Red Light Therapy Contraindications: Who Should Not Use It

Red light therapy has a remarkably strong safety record across hundreds of clinical trials. But no therapy is appropriate for everyone, and photobiomodulation is no exception. Certain medical conditions, medications, and circumstances require caution — and in a few cases, avoidance.

This guide divides contraindications into absolute (do not use), relative (use with medical guidance), and precautionary (be aware and monitor). Every recommendation is grounded in published research and recognised medical guidance.

Absolute Contraindications

These are situations where red light therapy should not be used over the affected area. The evidence or theoretical risk is sufficient to warrant avoidance.

Active Cancer Over Tumour Sites

This is the most frequently cited contraindication in the PBM literature, and it warrants careful explanation.

Photobiomodulation stimulates cellular metabolism, proliferation, and angiogenesis (new blood vessel formation). These are desirable effects in healthy tissue — they drive wound healing, collagen production, and tissue repair. In cancerous tissue, however, these same processes could theoretically accelerate tumour growth and metastasis.

The evidence is mixed and nuanced:

In vitro studies have shown that PBM can stimulate the proliferation of certain cancer cell lines (Sperandio et al., 2013, Journal of Biophotonics). However, other in vitro studies show growth inhibition at higher doses — reflecting the biphasic dose response.
Animal studies are similarly conflicting. Some show tumour promotion; others show no effect or even tumour suppression.
Clinical evidence is limited. Interestingly, PBM is widely used in oncology settings to treat oral mucositis caused by chemotherapy and radiation therapy, with no reports of tumour promotion in these clinical applications. The Mucositis Study Group of the Multinational Association of Supportive Care in Cancer (MASCC) recommends PBM for this purpose (Zadik et al., 2019, Supportive Care in Cancer).

The practical guidance: Do not irradiate known tumour sites or areas with active cancer. This is a precautionary position — the human evidence of tumour promotion is absent, but the theoretical mechanism is biologically plausible, and the stakes are too high for ambiguity. PBM use on areas distant from the tumour (e.g., treating oral mucositis during breast cancer treatment) appears safe based on current evidence.

If you are undergoing cancer treatment, discuss PBM with your oncologist before use.

Severe Photosensitivity Disorders

Certain genetic conditions involve pathological responses to light:

Xeroderma pigmentosum (XP) — a rare genetic disorder where DNA repair mechanisms for UV damage are defective. While XP primarily involves UV sensitivity, the extreme light sensitivity warrants avoiding all intense artificial light exposure.
Solar urticaria — hives triggered by sun exposure. Action spectra can extend into the visible red range in some patients.
Erythropoietic protoporphyria (EPP) — porphyrin accumulation causes severe pain on light exposure. The action spectrum includes visible light, including red wavelengths.

If you have any diagnosed photosensitivity disorder, consult a dermatologist before using red light therapy. The specific action spectrum of your condition determines whether red/NIR wavelengths are problematic.

Relative Contraindications

These are situations where red light therapy may be safe but requires medical guidance. The risk is either theoretical, condition-dependent, or manageable with appropriate precautions.

Pregnancy

There is no published evidence that red light therapy harms a developing foetus. However, there is also no controlled safety data in pregnant women — and for obvious ethical reasons, such studies are unlikely to be conducted.

What we know:

Red and NIR wavelengths do not carry enough energy to cause DNA damage (unlike UV)
Tissue penetration through the abdominal wall to reach the uterus would be minimal
PBM is used safely during pregnancy for conditions like carpal tunnel syndrome and back pain in some clinical settings

The precautionary position: Avoid irradiating the abdomen during pregnancy. Treating the face, extremities, or back (at safe distances from the abdomen) is likely safe but discuss with your obstetrician. Many clinicians take the view that the theoretical risk is negligible, but the conservative approach costs nothing. See our dedicated pregnancy guide for detailed discussion.

Epilepsy

The concern here is specific: pulsed or flashing light can trigger seizures in individuals with photosensitive epilepsy, which affects roughly 3% of people with epilepsy.

Continuous-wave (CW) devices — which emit a steady, non-flickering light — do not pose this risk. Most home-use LED panels and masks operate in continuous-wave mode and are safe for people with epilepsy.

Pulsed devices (those that intentionally pulse at specific frequencies, such as 10 Hz or 40 Hz) should be avoided by anyone with photosensitive epilepsy unless cleared by their neurologist. Some advanced panels offer pulsing modes — ensure these are disabled.

If you have epilepsy, check your device specifications. If it only operates in CW mode, the seizure risk is negligible. If it pulses, consult your neurologist.

Bipolar Disorder

Bright light therapy (typically 10,000 lux white light boxes) is an established treatment for seasonal affective disorder but has been associated with triggering manic or hypomanic episodes in individuals with bipolar disorder (Sit et al., 2007, Bipolar Disorders).

The relevance to red light therapy is uncertain:

Red/NIR devices operate at different wavelengths and lower visible intensities than bright light therapy boxes
The mechanism linking bright light to mania involves circadian clock manipulation via melanopsin receptors, which respond primarily to blue light (~480 nm), not red or NIR
No published case reports link red light therapy specifically to manic episodes

The precautionary position: If you have bipolar disorder, discuss RLT with your psychiatrist before use. The risk is likely very low, particularly with NIR-dominant devices, but monitoring is prudent during the first few weeks.

Thyroid Conditions

The thyroid gland is superficial and easily reached by red and NIR light. PBM has actually been studied as a treatment for thyroid conditions — a 2013 RCT by Höfling et al. in Lasers in Medical Science found that PBM reduced levothyroxine requirements in patients with autoimmune thyroiditis.

However, unsupervised thyroid irradiation could theoretically affect thyroid function — either beneficially or adversely. If you have Graves’ disease, Hashimoto’s thyroiditis, or other thyroid conditions:

Do not intentionally irradiate your thyroid without clinical supervision
If using a panel on your face or neck, this may incidentally expose the thyroid — discuss with your endocrinologist
Monitor thyroid function through regular blood tests if you begin regular neck-area treatments

Recent Cosmetic Procedures

After injectable treatments (Botox, dermal fillers, PRP), the treated tissue is in an acute inflammatory state. Adding PBM immediately could theoretically:

Increase filler metabolism through enhanced circulation
Alter Botox diffusion patterns
Increase bruising risk due to vasodilation

Wait 48–72 hours after Botox or fillers before resuming facial RLT. Some practitioners recommend a full week. After more invasive procedures (laser resurfacing, chemical peels, microneedling), wait until the acute healing phase is complete — typically 3–7 days, depending on the procedure.

Paradoxically, PBM is sometimes used deliberately after cosmetic procedures to accelerate healing. This should be done under clinical guidance with appropriate dosing.

Medication Interactions

Photosensitising medications are the most clinically significant interaction with red light therapy. These drugs increase skin sensitivity to light, potentially causing exaggerated redness, burns, or rashes at doses that would normally be safe.

High-Risk Medications

Medication	Drug class	Photosensitivity mechanism
Doxycycline	Tetracycline antibiotic	Phototoxic — generates ROS on light exposure
Tetracycline	Tetracycline antibiotic	Phototoxic
Minocycline	Tetracycline antibiotic	Phototoxic + photoallergic
Isotretinoin (Accutane)	Retinoid	Thins the stratum corneum, increasing light penetration
Tretinoin (topical)	Retinoid	Same mechanism as isotretinoin, localised
Methotrexate	Immunosuppressant / DMARD	Phototoxic in a subset of patients
Amiodarone	Antiarrhythmic	Highly phototoxic; accumulates in skin
Hydrochlorothiazide	Thiazide diuretic	Phototoxic
Fluoroquinolones (ciprofloxacin, levofloxacin)	Antibiotic	Phototoxic
St. John’s wort	Herbal supplement	Contains hypericin, a potent photosensitiser

Moderate-Risk Medications

NSAIDs (ibuprofen, naproxen, piroxicam) — piroxicam is the most photosensitising; ibuprofen is low risk
Certain antipsychotics (chlorpromazine, thioridazine) — phenothiazine-class drugs are photosensitising
Sulfonamide antibiotics — moderate phototoxic risk
Voriconazole — antifungal with significant photosensitivity risk
5-aminolevulinic acid (ALA) — used in photodynamic therapy; extreme photosensitiser by design

What to Do If You Take a Photosensitising Medication

Check the list — if your medication appears above, do not start RLT without consulting your prescriber
Start with a test patch — if your doctor approves, begin with a very short session (2–3 minutes) on a small area and observe for 24 hours
Use lower doses — reduce your target dose by 50% compared to standard protocols
Monitor closely — any unusual redness, blistering, rash, or itching means stop immediately

For a comprehensive list, see our dedicated medications page.

Medical Conditions Requiring Caution

Lupus (Systemic Lupus Erythematosus — SLE)

Photosensitivity is a hallmark of lupus — it is one of the 11 ACR diagnostic criteria. UV exposure can trigger lupus flares, and some patients are sensitive across the visible spectrum.

The relevance to red/NIR therapy is debated:

Most lupus photosensitivity is UV-mediated (primarily UVB, 280–315 nm)
Red (620–700 nm) and NIR (700–1100 nm) wavelengths are far from the UV spectrum
There are no published reports of lupus flares triggered specifically by red or NIR light

However, given that individual photosensitivity spectra vary and that lupus flares can be severe, the precautionary approach is warranted. If you have lupus, consult your rheumatologist before use. Consider a small test area and monitor for 48 hours.

History of Melanoma or Skin Cancer

If you have a personal history of melanoma, discuss RLT with your dermatologist before use. The concern is the same as with active cancer — theoretical stimulation of residual malignant cells — though the risk is likely lower in patients who have been treated and are in remission.

Do not use red light therapy directly over:

Previous melanoma excision sites
Dysplastic naevi (atypical moles)
Any suspicious skin lesions

Continue regular dermatological surveillance regardless of RLT use.

Pacemakers and Implanted Electronic Devices

Red and near-infrared light does not interfere with electronic devices — it is non-ionising electromagnetic radiation at wavelengths far from those that could induce currents in electronic circuits. There is no published evidence of pacemaker malfunction from PBM.

However, some caution is warranted:

Do not place contact devices directly over a pacemaker or implanted defibrillator site
The concern is not electromagnetic interference but potential heating of the metal casing
At panel distance (15+ cm), the risk is negligible

If you have an implanted electronic device, the pragmatic approach is to avoid prolonged, direct irradiation of the implant site. Treating other body areas is unproblematic.

Haemorrhagic Conditions and Anticoagulant Therapy

PBM increases local blood flow through nitric oxide-mediated vasodilation. In patients with bleeding disorders or those taking anticoagulants (warfarin, DOACs, heparin), this could theoretically increase bleeding risk at treatment sites.

In practice, this is a very low risk for external light therapy. It is more relevant for laser-based treatments that penetrate deeply. Standard LED panel use is unlikely to cause clinically significant bleeding. However, if you are on anticoagulation therapy and treating over surgical sites, wounds, or areas prone to bruising, monitor closely.

Children and Elderly

Children

The paediatric PBM literature is limited. Red light therapy has been studied in children for:

Neonatal jaundice (using blue light, a related phototherapy)
Oral mucositis during childhood cancer treatment (Soares et al., 2019, Pediatric Blood & Cancer)
Orthodontic pain management

No serious adverse events have been reported in paediatric studies. However, children’s skin is thinner and potentially more sensitive. If using PBM in children:

Reduce session times by 30–50%
Use lower irradiance settings or increase distance
Always supervise sessions
Ensure eye protection is worn and fits properly
Consult a paediatrician first, particularly for children under 12

Elderly

Older adults are generally good candidates for PBM. Ageing skin is thinner, which may actually improve light penetration to target tissues. However:

Medication interactions are more likely — older adults take more medications, many of which are photosensitising (see medication section above)
Skin fragility — very thin, fragile skin (common in those on long-term corticosteroids) may be more susceptible to thermal effects from contact devices
Cognitive considerations — ensure the person can communicate discomfort and operate the device safely

The published evidence on PBM in elderly populations is generally positive, particularly for wound healing, pain management, and cognitive support (Saltmarche et al., 2017, Photomedicine and Laser Surgery).

Eye Conditions and When Goggles Are Mandatory

The eye is the organ most vulnerable to light-based injury. The lens focuses incoming light onto the retina, concentrating energy density significantly.

When Goggles Are Mandatory

Any session where the device faces your eyes, regardless of wavelength
All NIR sessions — near-infrared is invisible; your pupil does not constrict in response
All sessions using devices with irradiance >50 mW/cm² at eye level
Children’s sessions — always, without exception

Specific Eye Conditions

Macular degeneration — interestingly, PBM is being actively researched as a treatment for age-related macular degeneration (AMD). The LIGHTSITE clinical trials (Markowitz et al., 2020, Ophthalmology) showed promising results. However, this uses carefully controlled, low-dose, specific-wavelength protocols applied by clinicians — not high-powered home panels.
Glaucoma — no specific contraindication, but eye protection is still required during body treatments
History of retinal detachment — wear goggles. The thermal effects of intense light on compromised retinal tissue are unpredictable
Post-cataract surgery — the artificial lens has different transmission characteristics. Consult your ophthalmologist before exposing the eye area to PBM

For comprehensive guidance, see our eye protection page.

When to Consult a Doctor First

You should discuss red light therapy with a healthcare professional before starting if you:

Have any form of cancer, current or in remission
Take any medication listed in the photosensitising section above
Have a diagnosed photosensitivity disorder
Are pregnant or planning to become pregnant
Have lupus, dermatomyositis, or other autoimmune conditions with photosensitive components
Have epilepsy and your device has a pulsing mode
Have bipolar disorder
Have an implanted electronic medical device
Have a thyroid condition and plan to treat the neck area
Have active skin infections, open wounds, or suspicious lesions at the treatment site

This is not an exhaustive list. When in doubt, ask. Most GPs and dermatologists are familiar with phototherapy in general terms, though they may need educating on the differences between PBM and UV phototherapy.

What FDA and Medical Bodies Say

FDA (United States)

The US Food and Drug Administration classifies most home-use LED red light therapy devices as Class II medical devices — the same risk category as powered wheelchairs and pregnancy test kits. This classification indicates the FDA considers them to present moderate risk when used as directed.

Several specific devices have received FDA clearance (510(k)) for indications including:

Temporary relief of minor muscle and joint pain
Temporary increase in local blood circulation
Treatment of mild to moderate acne (blue/red combination devices)

FDA clearance does not mean the FDA has found the device effective for every claim a manufacturer makes. It means the device is substantially equivalent to a previously cleared device and is considered safe for its stated indications.

NICE (United Kingdom)

The National Institute for Health and Care Excellence has not published specific guidelines on home-use PBM devices. However, NICE does recognise low-level laser therapy (LLLT) for certain indications, including oral mucositis management during cancer treatment (NICE guideline NG197).

MASCC/ISOO (International)

The Multinational Association of Supportive Care in Cancer and the International Society of Oral Oncology recommend PBM for the prevention of oral mucositis in patients undergoing certain cancer treatments. This is arguably the strongest institutional endorsement of PBM from a major medical body (Zadik et al., 2019).

World Association for Photobiomodulation Therapy (WALT)

WALT publishes recommended treatment doses for various conditions. These dosing guidelines are widely referenced in the clinical literature and form the basis for many of the protocols recommended on this site.

Frequently Asked Questions About Contraindications

Can I use red light therapy if I have had cancer in the past?

If you are in remission and your oncologist is satisfied with your surveillance, RLT on areas distant from the previous tumour site is likely safe. However, avoid irradiating the site of the previous cancer and discuss your plans with your oncologist. The concern is theoretical — no human clinical evidence shows tumour recurrence triggered by PBM — but the precautionary principle is appropriate for cancer.

Is red light therapy safe during breastfeeding?

There is no evidence of harm to breastfeeding mothers or infants from maternal RLT use. The photons do not affect breast milk composition. Avoid irradiating the breast tissue directly if you have any concerns, and consult your midwife or GP if uncertain.

Can I use red light therapy after drinking alcohol?

Alcohol causes vasodilation, as does PBM. The combination may increase flushing, dizziness, and headache. It is not dangerous, but it is suboptimal. For best results and comfort, avoid sessions immediately after drinking.

What about tattoos and red light therapy?

Tattooed skin absorbs more light than untattooed skin because tattoo pigments (particularly dark colours) absorb across the visible spectrum. This means tattooed areas may warm up more during treatment. This is generally safe, but monitor for excessive heat. If the tattooed area becomes uncomfortably warm, increase your distance from the device.

There is no evidence that red light therapy fades tattoos — the wavelengths used in PBM are different from those used in laser tattoo removal (which uses very high-powered, short-pulse lasers at specific wavelengths).

Summary

Red light therapy is contraindicated in very few situations. The key points:

Do not irradiate active tumour sites — precautionary, but non-negotiable
Severe photosensitivity disorders require specialist advice before any use
Photosensitising medications are the most common real-world concern — check the list
Pregnancy warrants caution over the abdomen, but treatment of other areas is likely safe
Epilepsy is only relevant for pulsed devices, not continuous-wave
Always protect your eyes, especially from NIR
When in doubt, ask your doctor — bring this article if they are unfamiliar with PBM

The overwhelming majority of people can use red light therapy safely. Understanding the small number of genuine contraindications allows you to proceed with confidence — or to seek appropriate medical guidance before starting.

This article is for educational purposes only and does not constitute medical advice. If any of the conditions listed above apply to you, consult a qualified healthcare professional before beginning red light therapy. For side effects and what to expect, see our side effects guide.