Antipruritic effects of transient heat stimulation on histaminergic and nonhistaminergic itch

Short-term Heat Application Reduces Itch Intensity in Atopic Dermatitis: Insights from Mechanical Induction and Real-life Episodes

Heat application is known to activate transient receptor potential (TRP) channels, which play a crucial role in sensory perception, including itch. In this study, the effect of a 5-s, 49°C heat application on itch intensity in atopic dermatitis (AD) patients was evaluated. The study comprised 2 parts: a controlled trial investigating the impact of brief heat treatment on mechanically induced itch, and a real-life study of AD patients experiencing itch attacks. A significant and immediate reduction in itch sensations following heat application was shown, with effects enduring over time. This response, however, showed notable individual variability, underscoring the potential of personalized approaches in AD treatment. Repeated applications of heat showed no habituation effect, suggesting its viability as a non-pharmacological, patient-tailored option for managing itch in AD. Further research in larger cohorts is warranted to refine treatment protocols and deepen understanding of the mechanisms involved.

Efficacy of Concentrated Heat for Treatment of Insect Bites: A Real-world Study

Insect bites that cause itch, pain and swelling are very common. The use of concentrated heat for relief of these symptoms may be a promising approach; however, the scientific evidence for efficacy of hyperthermia treatment is sparse. We report here the results of a large real-world study using a randomized control group to assess the efficacy of hyperthermia on insect bites in real-world conditions, specifically considering mosquito bites as the most common type. The study was conducted in a decentralized manner via a smartphone-controlled medical device, heat it®, for treatment of insect bites and stings through application of heat. The application that controls the device was accompanied by additional questionnaires, that collected data related to insect bites, such as itch and pain intensity. Analysis of data from over 12,000 collected treated insect bites, generated by approximately 1,750 participants (42% female, 39 ± 13 years) showed significant inhibition of itch and pain for all investigated insect species (mosquitoes, horseflies, bees and wasps). Mosquito bite-induced itch was reduced by 57% within the first minute and by 81% 5-10 min after treatment, and the overall reduction in itch and pain was more pronounced than in the control group. In conclusion, the results indicate that local application of heat relieves symptoms of insect bites.

Mild Skin Heating Evokes Warmth Hyperknesis Selectively for Histaminergic and Serotoninergic Itch in Humans

Chronic itch can severely affect quality of life. Patients report that their chronic itch can be exacerbated by exposure to warm conditions (“warmth hyperknesis”). The aim of this mechanistic study was to investigate the effect of mild heating of the skin in humans on various experimental models of itch. A total of 18 healthy subjects were recruited to the study. Itch was provoked by histamine, serotonin, or cowhage in 3 different sessions. The provoked area was heated with an infrared lamp, and the skin temperature was either not altered, or was increased by 4°C or 7°C. Subsequent to induction of itch, the itch intensity was recorded for 10 min while the skin was heated continuously throughout the entire period of itch induction. Heating the skin resulted in a significant increase in itch intensity when provoked by histamine or serotonin. It is possible that thermoception and pruriception interact and selectively produce a higher itch intensity in histaminergic and serotoninergic itch.