A recent study illustrated the dissimilarities in the impact of high-intensity laser therapy (HILT) on the skin surface temperature and vein diameter of the lateral fetlock joint region in a batch of racehorses with pigmented and nonpigmented skin in the treatment area. 

Twenty Thoroughbreds were divided into pigmented and nonpigmented skin groups equally and rendered the same HILT treatment. Both immediately before and after HILT, the thermographic examination was carried out to measure the skin surface temperature and an ultrasonographic examination to assess the lateral digital palmar vein diameter. 

The results were as follows:

• Skin surface temperature increased in the pigmented, while it decreased in the nonpigmented skin after HILT, with a marked difference between both groups. 
• The vein diameter increased in both pigmented as well as nonpigmented skin after HILT; however, without a marked difference between both groups.

Thus, it is clear that the melanin content in the epidermis has a pivotal role in light energy absorption and photothermal effects. The vein diameter changes after HILT application suggested that this increase may partly rely on photothermal mechanisms emerging in irradiated tissue. To describe the physiological and clinical effects of HILT further research is warranted.

Source: ZieliÅ„ska P, Soroko M, Howell K, et al. Comparison of the effect of high-intensity laser therapy (HILT) on skin surface temperature and vein diameter in pigmented and non-pigmented skin in healthy racehorses. Animals (Basel). 2021;11(7):1965.