Soft Laser Therapy Contraindications and Safety Information
Soft laser therapy (LLLT/photobiomodulation) is one of the safest physical therapy methods – but that does not mean it is suitable for everyone and every situation. If you use a home softlaser device, or are planning to buy one, it is important to know the contraindications and the rules for safe use.
In this article I summarize when NOT to use a soft laser, what precautions to take, and what side effects you can expect – based on scientific research and professional guidelines.
Why is soft laser therapy so safe?
The soft laser therapy is fundamentally different from surgical lasers. Devices intended for home use belong to Class IIIb (power below 500 mW) and do not produce heat in tissues – which is why they are also called "cold lasers."
The mechanism of action is photochemical, not thermal: light acts on the cells' mitochondria, increases ATP production and modulates inflammatory processes. Clinical trials for decades have consistently confirmed the method's favorable safety profile.
A 2019 systematic review (Zadik et al.) that examined the use of soft lasers in cancer patients found no evidence of serious side effects or tumor-promoting effects. A similar conclusion was reached in a 2023 review (Glass et al.) that analyzed aesthetic applications.
Absolute contraindications – When the soft laser is FORBIDDEN
The following situations are not recommended or are strictly forbidden for soft laser application:
1. Directing the beam into the eye
This is the only truly ABSOLUTE contraindication. Laser light – even low-power – can potentially damage the retina if directed straight into the eye.
Rule: Never point the laser head at the eye, and always use protective goggles (provided with the device). Both the patient and the operator should wear eye protection.
Important note: most therapeutic lasers emit a divergent beam, which reduces the risk with distance. Manufacturers are required to provide the Nominal Ocular Hazard Distance (NOHD) in the user manual.
2. Over a known malignant tumor
Do not treat directly over a tumor area, except when:
- for pain relief in terminal stages – with medical approval
- to manage side effects of cancer treatment (e.g. oral mucositis, radiation dermatitis) – under oncologist supervision
The scientific literature shows mixed results about the effect of soft lasers on tumor cells. While there is no clear evidence that they stimulate tumor growth, caution is warranted. If you are being treated for cancer, always consult your treating physician.
3. Over an active purulent infection
Do not treat infected, purulent wounds or abscesses with a soft laser. Increased blood flow and cellular activity may potentially promote the spread of infection. The infection should be treated first, and the soft laser may be used afterwards to support healing.
Relative contraindications – Increased caution required
In the following cases the soft laser is not necessarily forbidden, but requires increased care:
Pregnancy
There are no long-term safety studies on the effect on the fetus. Therefore, avoid treating the abdomen and lower back during pregnancy.
Treatment of other body parts (e.g. limbs, shoulder) is generally allowed, but consult your obstetrician-gynecologist.
Epilepsy (photosensitive type)
Pulsed light can provoke seizures in some people with epilepsy. If you have photosensitive epilepsy, speak with your neurologist before use.
Cardiac pacemaker
Although there is no scientific evidence that soft lasers interfere with pacemaker function, some manufacturers and professional organizations recommend avoiding application directly over the heart area as a precaution. If you have a pacemaker, consult your cardiologist.
Thyroid area
The thyroid is sensitive to light therapy. Prolonged treatment of the anterior neck region may potentially overstimulate the thyroid, leading to increased thyroxine production. If you have thyroid problems (hyper- or hypothyroidism), avoid this area or consult an endocrinologist.
Bleeding disorders, anticoagulant use
Soft lasers increase local circulation. In hemophiliacs or those taking anticoagulants this could potentially be an issue. Research has not shown a significant risk, but increased caution is advised.
Fresh trauma, active bleeding
In the first 24–48 hours after an acute injury – when active bleeding or severe swelling is present – wait until the acute phase has passed. Afterwards, the soft laser can support healing.
Photosensitizing conditions and medications
Certain medications and conditions increase skin photosensitivity:
- Tetracyclines, fluoroquinolones (antibiotics)
- Certain NSAIDs
- Amiodarone (cardiac drug)
- Photosensitive skin diseases (lupus, porphyria)
If you are taking such medications or have such a condition, consult your doctor before using a soft laser.
Tattoos, moles, pigmented skin areas
Dark pigments (tattoos, moles, very dark skin – Fitzpatrick V–VI) absorb more laser light, which can cause local heating. Be extra cautious on these areas and reduce energy density or avoid the area.
Use in children?
Yes, soft lasers can be used in children. There is no scientific evidence that they are harmful to the developing organism, including growth plates (epiphyseal plates).
Doses should be adjusted to the child's body weight and the size of the treated area – generally a lower energy density is used.
Possible side effects
The side effect profile of soft laser therapy is extremely favorable. According to the literature, the following mostly mild and transient side effects may occur:
| Side effect | Frequency | Action |
|---|---|---|
| Mild sensation of warmth | Common, normal | No intervention needed |
| Transient skin redness | Occasional | Resolves on its own |
| Temporary increase in pain | Rare, after 1–2 treatments | Reduce the dose |
| Mild dizziness | Very rare | Rest, continue cautiously |
| Headache (transcranial application) | Rare | Reduce time/dose |
Important: Clinical trials have not reported serious, lasting side effects related to soft laser therapy. The favorable safety profile is one of the main reasons it is increasingly popular for home use as well.
Summary of safety rules
By following the basic rules below you can safely use a home softlaser device:
Always do
- Wear protective goggles – Always wear the protective goggles supplied with the device
- Read the user manual – Every device is different, know yours
- Apply to clean, intact skin – Avoid infected or damaged areas
- Follow the recommended dose – More is not always better
- Consult a doctor – If you have any chronic diseases
Never do
- Point at the eye – Never, under any circumstances
- Treat over a tumor – Without medical approval
- Treat a purulent wound – Treat the infection first
- Overdose – "More = better" does not apply here
Professional guidelines and recommendations
Several professional organizations have issued guidelines on the safe use of soft lasers:
- WALT (World Association for Photobiomodulation Therapy) – Dosage recommendations and safety protocols
- NAALT (North American Association for Laser Therapy) – Contraindication consensus (2010)
- FDA – Classification and safety requirements for Class IIIb lasers
- IEC 60825 – International standard for safe laser use
CE-marked devices marketed in Europe comply with the MDR (Medical Device Regulation) requirements and can be used safely in a home environment.
Frequently asked questions about contraindications
Can I use a soft laser if I take medication?
Most medications are not a contraindication. Exceptions are photosensitizing agents (certain antibiotics, amiodarone). If unsure, consult your pharmacist or doctor.
What if I had cancer before but am considered cured?
Current evidence does not support that soft lasers increase the risk of cancer recurrence. A 2023 systematic review (Glass et al.) found no association between photobiomodulation and tumor recurrence. Nevertheless, it is worth consulting your oncologist, especially if you want to treat the area of a previous tumor.
Can I use it if I have diabetes?
Yes, diabetes itself is not a contraindication. In fact, soft laser therapy may help wound healing in diabetic foot ulcers – this is an active research area with positive results.
What should I do if pain increases after treatment?
This can rarely occur after the first 1–2 treatments – the so-called "healing reaction." It usually resolves within 24–48 hours. If persistent, reduce the dose or skip treatment for a few days.
Summary – Quick overview
What is this article? A comprehensive guide to contraindications and safety information for soft laser therapy.
Who is it for? Anyone using or planning to buy a home softlaser device, and healthcare professionals.
Main message: Soft laser is one of the safest physical therapy methods, but there are situations where it is not recommended or should be used cautiously. The only absolute contraindication is directing it at the eye.
Key points:
- ABSOLUTELY FORBIDDEN: pointing at the eye, treating directly over an active tumor (without medical approval), treating purulent infections
- CAUTION: pregnancy (abdomen/lower back), pacemaker, thyroid, photosensitizing conditions
- SIDE EFFECTS: rare, mild, transient
- Always wear protective goggles!
Recommended softlaser devices
If you are looking for a safe, CE-certified home softlaser device, check out our range:
Softlaser devices at Medimarket.hu →
All devices we sell comply with European medical device regulations (MDR) and come with detailed Hungarian-language user manuals.
Sources
- Zadik Y, et al. (2019). Tumor safety and side effects of photobiomodulation therapy used for prevention and management of cancer treatment toxicities: A systematic review. Support Care Cancer. PubMed: 31109692
- Glass GE, et al. (2023). Photobiomodulation: A Systematic Review of the Oncologic Safety of Low-Level Light Therapy for Aesthetic Skin Rejuvenation. Aesthet Surg J. PubMed: 36625556
- Chung H, et al. (2012). The Use of Low Level Laser Therapy (LLLT) For Musculoskeletal Pain. MOJ Orthop Rheumatol. PubMed: 25364648
- Zein R, et al. (2018). Review of light parameters and photobiomodulation efficacy. J Biomed Opt. PubMed: 30550048
- WALT (World Association for Photobiomodulation Therapy). Dosage recommendations. waltpbm.org
The information in this article is for guidance only. Home therapeutic devices are intended to complement medical treatment and do not replace specialist care. If you have any chronic condition or are unsure about contraindications, consult your treating physician.
