The efficacy of products with rubefacients is poorly understood as there is very little data on how they work following application on the skin. Typical rubefacients, such as menthol, camphor, capsaicin, aescin, arginine, etc., are most commonly found in sports cosmetics and musculoskeletal pain relief products, which when applied on the skin, are thought to cause vasodilatation and increased blood flow to the skin by activating temperature-sensitive receptors.
In addition to the many methods that determine skin blood flow directly, others measure variables indicating changes in skin blood flow. Thus, within performed in vivo study, the efficacy of products with rubefacients was evaluated indirectly by measuring change in skin temperature, using a thermal imaging camera that utilises the appearance of infrared radiation on the surface of the skin. In the thesis, the effect of four different products, differing in the incorporated rubefacient (menthol, camphor, capsaicin), technological form (hydrogel, lipophilic cream) and product group (cosmetic product, medical aid, nonprescription medicine), on skin temperature was evaluated.
The results showed that products with menthol had the same time-dependent effect, i.e. a statistically significant decrease in skin temperature immediately after application compared to the basal value, and a statistically significant increase in skin temperature five minutes after application compared to the values immediately after application. The same trend of temperature changes was observed while testing the product which, in addition to the menthol, contained camphor. The product with capsaicin did not cause statistically significant changes in skin temperature during the measurements. Statistically significant differences in skin temperature change between the products were observed during the first five minutes and are most likely due to the different composition or technological formulation of the products. In conclusion, thermography as a complementary technique for skin temperature evaluation represents an innovative and promising method for monitoring the efficacy of rubefacients in further studies.
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