I first summarized the scant evidence concerning low-level or “cold” laser therapy in companion animals in 2010, and I reviewed a couple of small studies in 2011. A recent checked showed only a couple of studies looking at cold laser since. All of these were small trials, and I am not able to access the full reports, so I cannot thoroughly evaluate the quality of the study design or conduct. None of these studies provide a definitive answer to the usefulness of laser therapy for the problems evaluated, but since we must work with the evidence we have rather than the evidence we would like, I thought I would briefly discuss this new research.
The first is a study from India looking at laser effects on wound healing in dogs.
Efficacy of low level LASER therapy on wound healing in dogs. Indian Journal of Veterinary Surgery 2011 32 2 103-106 Singh, M., Bhargava, M. K., Sahi, A., Jawre, S., Singh, R., Chandrapuria, V. P., Kocchar, G.
The study was undertaken to assess the efficacy of low level LASER therapy on wound healing in 30 dogs. The dogs were randomly divided into five groups, each consisting of six dogs. The dogs of group 1 were treated as control, whereas the dogs of groups II, III, IV and V were treated with low level LASER therapy for 2 min, 10 Hz, 1.2 Joules; 4 min, 10 Hz, 2.4 Joules; 2 min, 30 Hz, 1.2 Joules; and 4 min, 30 Hz, 2.4 joules, respectively. The clinical parameters were recorded on day 0 (control) and subsequently on days 3rd, 5th, 7th, 10th and 14th in the animals of all groups. Increased healing percentage, decreased inflammation and exudation with clinically no scab during healing and minimal scar at wound site after healing, early regeneration of granulation tissue, better organization, compactness and intense epithelial regeneration were observed in dogs treated with laser therapy as compared to control animals. Significant increase in rectal temperature with non-significant variation in pulse and respiratory rates were observed in all the groups. The maximum decrease in the size of the wounds was observed in groups III and V, with a maximum healing rate of 94.84% and 88.01%, respectively up to 14 days, with maximum efficacy at 4 min, 10 Hz, 2.4 joules protocol followed by 4 min, 30 Hz, 2.4 joules.
The groups were small, it is unclear if the assessment was blinded, the outcome measures appear to be subjective, and there is no reported statistical analysis to indicate how likely it is that the differences between the groups are due to chance. The authors report a beneficial effect from the laser therapy, but again how reliable this conclusion is cannot be determined from the available information.
The next study was also done in India and evaluated laser therapy for wound healing in dogs.
Madhya Pradesh Pashu Chikitsa Vishwavidyalaya, Jabalpur, MP, India. Low level laser therapy for the healing of contaminated wounds in dogs: histopathological changes. Indian Journal of Veterinary Surgery. 2013 34 1 57-58
The study was conducted on 18 dogs, divided into three groups comprising of 6 animals each. In group 1 – dressing of contaminated wounds was done with antiseptic liquid and antibiotic injected parenterally. In group 2, dressing of contaminated wound was done+low level laser therapy (10 Hz+5 min, 3 Joule, for 5 consecutive days)+parenteral antibiotic. In group 3, dressing of contaminated wound was done along with low level laser therapy (20 Hz+10 min, 6 Joule, for 5 consecutive days)+parenteral antibiotic. The biopsy punch was collected from the site on days 0 and 14. No apparent differences could be observed between the non-laser treated group and the laser treated groups with respect to histopathological examination except for the thicker epidermis noticed in five cases of the laser treated group as compared to that in non-laser treated group. It was concluded that low level laser therapy has no significant effect on healing of contaminated wounds in dogs.
Like the previous study, this was a small trial with limited information available about how it was conducted. This study, unlike the first, did not find any benefit from laser therapy on wound healing.
The evidence in humans is mixed and inconclusive on the benefits of lasers for facilitating wound healing, so while some benefit is possible, it is not yet clear if there actually is a clinically meaningful benefit in dogs.
The third article evaluated laser therapy for reducing foot itching in dogs with environmental allergies.
Stich AN, Rosenkrantz WS, Griffin CE. Clinical efficacy of low-level laser therapy on localized canine atopic dermatitis severity score and localized pruritic visual analog score in pedal pruritus due to canine atopic dermatitis. Vet Dermatol 2014 Oct;25(5):464-e74. doi: 10.1111/vde.12144. Epub 2014 Jun 9.
Canine atopic dermatitis is a genetically predisposed inflammatory skin disease often requiring multimodal treatment. There is a need to find further low-risk adjunctive therapies.
To evaluate the localized effect of low-level laser therapy (LLLT) on the paws of dogs with atopic dermatitis using a localized canine atopic dermatitis severity score (LCADSS) and owner localized pruritic visual analog score (LPVAS) in comparison to treatment with a placebo.
Thirty client-owned dogs with symmetrical pedal pruritus due to canine atopic dermatitis.
Dogs were randomly assigned into two groups. In each group, one paw was treated with LLLT and one paw treated with a placebo laser (comparing either both fore- or hindpaws). Treatments were administered at 4 J/cm(2) (area from carpus/tarsus to distal aspect of digit 3) three times per week for the first 2 weeks and two times per week for the second 2 weeks. Scores were assessed for each paw at weeks 0, 2, 4 and 5.
There were no significant differences in LCADSS or LPVAS between LLLT and placebo treatments between weeks 0 and 5 (P = 0.0856 and 0.5017, respectively). However, LCADSS and LPVAS significantly decreased from week 0 at weeks 2, 4 and 5 in both LLLT and placebo groups (P < 0.0001 for all).
CONCLUSIONS AND CLINICAL IMPORTANCE:
Low-level laser therapy is not an effective localized treatment for pedal pruritus in canine atopic dermatitis.
The study appears to have been well-controlled, though there is no mention of blinding, and the outcome measures are subjective but commonly standardized assessment tools. The study found improvement on both active and placebo treatment, which is almost always the case in clinical trials involving skin allergies, but did not see any benefit of laser beyond that of the placebo.
Finally, another dermatology study looked at cold laser therapy for an ill-defined set of disorders in which dogs have inadequate hair growth. Since the cause of these problems is not understood, and there is no well-demonstrated effective treatment, something like cold laser may be worth trying even without a solid reason to think it will be of benefit.
Olivieri L, Cavina D, Radicchi G, Miragliotta V, Abramo F. Efficacy of low-level laser therapy on hair regrowth in dogs with noninflammatory alopecia: a pilot study. Vet Dermatol. 2015 Feb;26(1):35-9, e11. doi: 10.1111/vde.12170. Epub 2014 Sep 16.
Canine noninflammatory alopecia (CNA) is a heterogeneous group of skin diseases with different underlying pathogenesis. The therapeutic approach is challenging, and new options for treatment are desirable.
To test the clinical efficacy of low-level laser therapy (LLLT) on hair regrowth in CNA.
Seven dogs of different ages, breeds and genders with a clinical and histopathological diagnosis of noninflammatory alopecia.
Each dog was treated twice weekly for a maximum of 2 months with a therapeutic laser producing the following three different wavelengths emerging simultaneously from 21 foci: 13 × 16 mW, 470 nm; 4 × 50 mW, 685 nm; and 4 × 200 mW, 830 nm. The fluence given was 3 J/cm(2) , frequency 5 Hz, amplitude of the irradiated area was 25 cm(2) and application time was 1.34 min. A predetermined alopecic area was left untreated and served as a control area. From one dog, post-treatment biopsies of treated and untreated sites were obtained for histological evaluation of hair density and the percentage of haired and nonhaired follicles.
At the end of the study, coat regrowth was greatly improved in six of seven animals and improved in one of seven. By morphometry, the area occupied by hair follicles was 18% in the treated sample and 11% in the untreated one (11%); haired follicles were (per area) 93% in the treated sample and only 9% in the control sample.
CONCLUSIONS AND CLINICAL IMPORTANCE:
Our clinical and histological data document promising effects of LLLT on hair regrowth in CNA. Further studies investigating the biological mechanism underlying the effect of LLLT on hair follicle cycling are warranted.
The results suggest laser therapy may have stimulated hair growth in these dogs. However, only 7 dogs were involved, and only one provided skin biopsies, so this study merely hints at the potential for laser therapy, and further work with appropriate controls would be needed to demonstrate there is real benefit to be had.
The research into cold laser in dogs and cats is sparse and generally low quality. Most studies are small and have minimal or uncertain controls for bias and error. Some show promising results, others do not. At this stage, as I concluded in my initial discussion of this topic, there is enough evidence to warrant further study but not enough to support routine clinical use of cold laser. If vets want to try this therapy, they have an obligation to be clear with client that the risks and benefits have not been established and that the treatment is essentially experimental. There is nothing wrong with using such a treatment given appropriate informed consent, but the aggressive marketing of laser equipment to vets as a profitable treatment is ethically questionable given the lack of good evidence that it is a truly safe and effective treatment for any condition.