Healing with light: laser therapy for dogs and cats

Low level laser therapy uses violet, green, red, and infrared wavelengths to reduce pain, support healing, and enhance cellular function in dogs and cats. 

Veterinarians use low level laser therapy (LLLT) in dogs and cats to reduce pain, inflammation, and edema. LLLT also promotes wound and nerve healing and prevents cell death and tissue damage. Over 40 years of research prove laser therapy’s efficacy. 

Yet LLLT remains underutilized in mainstream veterinary medicine. This is likely due to the wide variety of lasers on the market and a lack of education on laser therapy. This article will help you understand laser therapy for dogs and cats. It explains how lasers are classified and what conditions different wavelengths are used for. 

Understanding laser classification 

Experts classify lasers by wavelengths of light and power. They created this classification system to determine laser safety. It has nothing to do with efficacy. Therapeutic lasers in veterinary medicine include Class 2, 3B, and 4. 

• Class 2: This designation is “safe with a 0.25 sec aversion response.” Class 2 lasers feature low-powered visible light. They are safe as long as you can close your eyes. Violet, green, and red Class 2 lasers are available for use on dogs and cats. 
• Class 3B: Regulators automatically place infrared lasers in Class 3B or 4 because their light is invisible. This means they are a danger to the eyes. The Class 3B designation is “unsafe for eyes, generally safe for skin.” 
• Class 4: These high-powered infrared lasers are designated “unsafe for eyes, unsafe for skin.” Class 4 lasers generate enough heat to burn. 

The Occupational Safety and Health Administration requires everyone in a room to wear eye protection (including the animal being treated) when Class 3B and 4 lasers are in use.

Different light wavelengths have different effects on the body

Violet light 

Researchers have studied the 405nm wavelength in the violet spectrum more than any other. This wavelength is slightly longer than ultraviolet (UV) light. Practitioners often use UV light as a disinfectant to kills many microorganisms. Violet light is also antimicrobial, killing many clinically important viruses, bacteria, and fungi. 

In addition, violet light enhances the immune system through the intracellular release of nitric oxide. This immune response is synergistic and more pronounced when violet light is paired with green light. 

Since violet light is directly antimicrobial and enhances immune response, it’s a good adjunct treatment for infections. It also spares the microbiome and can be combined with topical or herbal antibiotics to reduce systemic antibiotic use.

Decreasing broad spectrum antibiotic use helps prevent antibiotic resistance and microbiome dysbiosis (bacterial imbalance, especially in the gut). Studies show that violet light increases cellular respiration and can be used to enhance athletic performance. 

Violet light inhibits inflammatory mediators to decrease pain and swelling. The 405nm violet wavelength is very short and carries twice as much energy as infrared light. It should be used in low power doses only, at no more than 5mW. Even 15mW of violet light can damage osteoblasts.

Green light 

Green lasers were only introduced to the veterinary market in May 2024. Green light is best known for bone healing and stem cell proliferation and differentiation. Research shows that green light increases stem cell division, leading to more stem cells in the area lasered. 

Green light also promotes stem cells to change into a particular type of cell. Bones contain stem cells in the marrow. Lasering a broken bone with green light increases stem cells in the marrow. It then promotes their differentiation into osteoblasts — the cells that form new bone.

Additionally, green light opens calcium channels in osteoblasts, increasing calcium secretion and helping form a bony matrix. This process creates a callous that bridges bone fractures. Studies on green light show that it also helps nerves heal faster, especially when paired with violet light. 

Red and infrared light 

Red and infrared (IR) light work the same way in the body. Red light contains more energy per photon and spreads differently in the body. It produces a more systemic effect, while infrared light acts locally. 

Red/IR light are the best wavelengths for cellular proliferation, meaning they are the best for wound healing. Researchers have extensively studied these wavelengths for treating pain and inflammation, with consistently positive outcomes. Most dermal and musculoskeletal conditions would benefit from red/IR laser therapy. 

Some cautions must be taken with IR light because it generates heat and can burn tissues. Pigmented (black) skin experiences more complications, so treatment times should be decreased. 

Practitioners should avoid treating heat-sensitive tissues like the brain and glands. Glandular tissues make enzymes, peptides, and hormones that can be denatured by excessive heat. 

Clinicians should avoid the eyes and ensure everyone wears protection when using IR light. This precaution isn’t needed for red light, but wavelengths above 670nm (red into infrared) should be avoided in cancer cases. These wavelengths can cause malignant cell proliferation. Shorter wavelengths of red (635nm and lower) do not show this effect. 

Cancer is a failure of the immune system. Because violet and green increase immune response, these wavelengths may help treat cancer in dogs and cats. However, further study is needed.

Laser therapy for dogs and cats is safer than pharmaceuticals and, in many cases, may prevent the need for medications. Perhaps in the future, LLLT will become standard of care, where we laser first and use pharmaceuticals as an adjunct or complementary therapy.

The science behind laser therapy 

Understanding a little physics and biology is important to understanding laser therapy. 

A photon of light is a package of energy. Photon energy varies inversely with its wavelength — the shorter the wavelength, the more energy it holds. 

Visible light wavelengths contain more energy than infrared wavelengths because they’re shorter. Infrared light generates heat; visible light does not.

The first law of thermodynamics states that “energy cannot be created or destroyed, only transformed from one form to another.” Energy loss to heat in the infrared spectrum means these lasers are often high powered — typically 1,000–15,000mW (1–15W). 

Visible light lasers retain their energy, making them therapeutic at low power – i.e. 5-100mW (0.005-0.1W).

In high school biology, everyone learns that mitochondria are the “powerhouse” of cells. Like chloroplasts in plant cells, mitochondria in animal cells can absorb light and convert it into chemical energy, called ATP. 

Cells use ATP to fuel all the chemical reactions in the animal’s body. An increase in ATP enhances healing and cellular function by increasing the efficiency of cellular reactions. 

Chlorophyll has an absorption spectrum of most colors except green. Plant leaves absorb all light except green, so what we see is green. Different molecules in mitochondria absorb violet and green light. Red and infrared light work by increasing ATP production without being absorbed. 

LEDs vs. lasers

Devices made for at-home use with dogs and cats aren’t true lasers. They rely on red light therapy and use LEDs rather than lasers. Some also include LED infrared light. 

What’s the difference? Lasers produce coherent light while LEDs produce non-coherent light. The coherency of the light makes a therapeutic difference. While LEDs have some effect, and are generally safe, they are not as effective as lasers. 

In human medicine, clinical trials for 510(k) FDA clearance use an LED as the control when testing lasers for specific conditions like post-operative pain. Manufacturers must prove the laser is more effective than the LED.

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