
The skin has the remarkable capacity to respond to sensory thermoregulatory stimuli in tandem with the nervous system. Thermoregulation refers to the mechanisms of temperature fluctuation, along with the biological responses that occur within the body. Thermotherapy involves the application of cold (cryotherapy) or heat to induce changes in the cutaneous, muscle and soft tissue. Thermotherapy increases tissue temperature, improves blood flow, tissue metabolism and connective tissue extendibility.
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The skin has the remarkable capacity to respond to sensory thermoregulatory stimuli in tandem with the nervous system. Thermoregulation refers to the mechanisms of temperature fluctuation, along with the biological responses that occur within the body. Thermotherapy involves the application of cold (cryotherapy) or heat to induce changes in the cutaneous, muscle and soft tissue. Thermotherapy increases tissue temperature, improves blood flow, tissue metabolism and connective tissue extendibility.
Various applications of thermotherapy, ranging from frigid cold-water immersions to hot steam baths, have been applied throughout history to aid in the treatment of skin conditions, diseases and other comorbidities.
The History of Thermotherapy
One of the earliest accounts of thermotherapy dates back to ancient Rome. Roman baths were introduced as part of daily rituals and were established as communal public bathing facilities for the purpose of promoting health and wellness. The Diocletian was the largest of all of the Roman bath facilities and offered its signature treatment by beginning at the unctuarium for an oil application to the body, followed by a steam bath called the tepidatium, and commencing with the steaming caldarium bath. An instrument called a strigil was used on the skin as an exfoliating tool during the steam session. The session was completed with a cold bath immersion called the frigidarium.1,2
In fifth century B.C., Greek physician Hippocrates prescribed many variations of thermotherapy treatments as a primary healing modality, along with favoring baths in spring water among other humoral and water-based therapies. Perhaps one of the most famous earlier, innovative physician’s prescribing hydrotherapy techniques and water therapies was Monsignor Father Sebastian Kneipp (1821-1897). Kneipp had cured himself from tuberculosis with his water therapies and developed systemic and controlled applications of hydrotherapy as his “water cures.” His water therapies were based on hydrotherapy treatments with alternating water temperatures as well as pressures. His work became famed throughout the world, and entire families would seek his therapies and care at the Kneipp sanatorium (spa).3
The term spa is an acronym for the Latin phrase “Salus per Aquam” – health from water, and it is named after the town Spa, located in Belgium, where mineral springs were abundant. Further research reveals many historical accounts of early naturopaths, physicians and physiotherapists employing the activity of friction rubs on the body, alternating stimulus of hot and cold water, hydrotherapy, poultices and herbal packs. These philosophies and protocols were the predecessors to modern physiotherapy employed in the health and medical field today.
Skin Perception Fibers and Sensation
The skin serves as a primary sensory organ for external stimuli and stressors including cold, heat, pain, perception and mechanical pressure or tension, as well as various immune and inflammatory responses. Cutaneous nerve fibers sense changes in the kin’s temperature, pH and inflammation and, in turn, activate “messages” to the central nervous system (CNS). The three types of receptors thermoreceptors (heat and cold), nociceptor (pain) and mechanoreceptors (mechanical changes or pressure), are responsible for transmitting outside signals to the spinal cord and brain.
Nerve terminals throughout the body are often associated with receptors that may perceive a close sensory interaction. The brain then responds to these signals resulting in the responses in the skin. The ability to perceive changes in skin temperature depends on the location the body is stimulated, the amplitude and rate of temperature change and the baseline temperature of the skin. There is a great variation in sensitivity to changes in skin temperature across the body. The most sensitive receptor sites to temperature are the face, cheeks and lips with the average temperature of the skin being from 84.2°F to 98.6°F.
Sensory nerves are interconnected throughout the entire skin tissue as well as the subcutaneous layer. Most nerve fibers and endings are found in the mid-dermis and the papillary dermis. In the epidermis, sensory nerves are linked to keratinocytes, melanocytes, Langerhans cells and Merkel cells. The epidermal nerves consist of free nerve endings and the dermis features free sensory nerve endings and various corpuscles. Peripheral sensory nerves may respond by the velocity at which action potentials travel through the nerve fibers. These are classified as Aα(alpha), Aβ(beta), Aδ(gamma) and C fibers. Among them, Aβ and Aδ fibers are mostly mechanically sensitive. Nerves of the skin belong to a subset of sensory nerves that are both mechanical and heat-responsive C fibers. The C fibers are the predominant nerve pathway for thermoperception of warmth. Aδ fibers respond to gentle cooling, whereas selective C fibers become activated during extreme cold.
Thermal stimuli applied to the skin induce a variable degree of sensory perception. When decreasing the stimuli temperature, the quality of sensation may change from cool to cold, from icy cold to pain. Increasing the stimuli temperature can cause a change in the sensations from warmth, to heat, to sharp or dull pain. Once the temperature approaches 59°F, the perception of cold as well as pain is transmitted and is described as a burning, aching and pricking sensation. This delicate thermo-sensing process is also related to specific receptor proteins that are located within the free nerve endings in the skin, known as transient receptor potential (TRP), and areion channels located in the biomembrane.4
Sensitive skin is defined by unpleasant sensations such as burning, stinging, tingling, pricking or itching in response to various normal physical, chemical and thermal stimuli. These symptoms have led to the consideration of a potential dysfunction of the intra-epidermal nerve fibers that are responsible for pain, temperature and itch perception.
Recent studies suggest that sensitive skin could become assimilated to small fiber neuropathy. Keratinocytes also have sensory receptors present on neurons. Transient receptor potential TRPV1, is one of the main transducers of painful heat, which is also involved in itching, and receptor TRPV4 is a heat sensor. While TRPV1 and TRPV4 are expressed both by sensory neurons and keratinocytes, it has recently been demonstrated that selective activation of TRPV1 on keratinocytes is sufficient to induce pain. Similarly, the targeted activation of keratinocyte expressed TRPV4 elicits itch and the resulting scratching behavior.5
Mind the Nerves
Research has identified the connection between the trigeminal nerves and the close association regarding the innervation of facial muscles. Consideration should be given to clients with trigeminal neuralgia that may present pain within the sensory territory of the trigeminal nerve, and may affect other facial nerves, which is generally caused by nerve compression. Clients with trigeminal neuralgia may experience a burning sensation or shock type pain that can present as a sudden onset or last for several minutes.
As expressed earlier, the skin is symptomatic to pressures and temperatures that vary among individuals. Additionally, the density of the dermis, blood flow and circulation, and the hypothalamus function may allude as to why some individuals may respond differently to heat, cold and pressure than others. Subcutaneous tissues, especially fat, will insulate muscle tissues from cold and heat applications, adding individual variability in physiologic responses to modality application.6,7
As a primary consideration, in addition to pressure, applied heat or cold nerve sensitivity may also be impacted or increased by:
- Facial massage,
- Acupressure,
- Intra oral massage,
- Gua sha,
- Anatomical trigger points,
- Facial reflexology with steel tools,
- Migraines,
- Bell’s palsy,
- Thermotherapy,
- Cryogenics,
- Cryotherapy machines,
- Skin needling (all forms),
- All forms of electrotherapy currents,
- Heat generated devices (IPL, RF, HIFU),
- Pressure driven devices (Ultrasound),
- Dental and gum surgeries and implants
- Metal tooth fillings and posts,
- Neuropathy and nerve damage,
- Head, neck or spine injuries,
- TMJ,
- Nutrient deficiencies like vitamin B1, B12, E, B6 and D, as well as niacin, copper, calcium, magnesium and potassium. 8
Thermo Regulatory Hydrotherapy
Thermo Regulatory Hydrotherapy (TRH) is the use of water in any of its forms (i.e. water, ice, steam) by the utilization of water temperature fluctuations, duration, specific site applications and alternating stimulus. Many health benefits arise when the core temperature of the body is reduced and the skin’s surface is cooled by hydrotherapy. It is frequently used in physiotherapy and spa therapeutics. Hydrotherapy tubs, mineral bath immersions and other various forms of water therapies are frequently used (See Benefits of THR9, 10, 11, 12).
Alternating the Temperatures
The goal of thermotherapy is to alter tissue temperature in a targeted region over time for the purpose of inducing a desired biological response (See THERMOTHERAPY - WARM). The majority of thermotherapies are designed to deliver the thermal therapy to a target tissue volume with minimal impact on intervening or surrounding tissues. By increasing the temperature of the skin and soft tissue, the blood flow increases by vasodilation. The metabolic rate and the tissue extensibility will also increase.
Heat Therapy. Heat increases oxygen uptake and accelerates tissue healing, it also increases the activity of destructive enzymes, such as collagenase, and it increases the catabolic rate. Regarding temperature, in physiotherapy, the skin surface will generally perceive warmth between 92-98°F, and hot between 98-104°F. The therapeutic range for heat modalities ranges usually between 100-115°F. However, thermal damage can be caused as low as 107.6°F on certain individuals.
Care should be taken to test any steamed towel, or device on the wrist or with a digital infrared digital thermometer before applying to the face or body. Steaming the skin for five to seven minutes will not break capillaries, cause rosacea, shrink pores, cause the skin to become oilier, disrupt barrier function or induce hyperpigmentation. Caution should be taken to position the steamer at the proper height from the facial table, angle the device for full dispersion of steam, and ensure the steamer is placed at a suitable distance for client comfort.
Cold Therapy. Cryotherapy or cold therapy has been used in medicine for decades with great success, specifically in physical therapy, sports medicine and pain management (See CRYOTHERAPY - COLD). Cold applications cause vasoconstriction, which results in decreased tissue blood flow, and reduces tissue metabolism, oxygen utilization and inflammation.
Icing is used for the ability and intent to transfer thermal energy in a short time frame. Interestingly, there are varied responses with cryotherapy. By decreasing the temperature of the skin and soft tissue, the blood flow decreases by vasodilation. The vasodilation will be followed by a vascular action, which will prevent against hypoxic damage called the hunting reflex or reaction. For example, if a cold pack is left on the skin for more than 10 minutes, the blood vessels will dilatate.13 The tissue metabolism will decrease inflammation, conduction rate and tissue extensibility.
At temperatures of 86°F or lower, the activity of cartilage degrading enzymes, including collagenase, elastase, hyaluronidase, and protease, is inhibited. Many health benefits are provided by reducing the body’s core temperature and cooling the skin’s surface, particularly through cold water compression, skin icing, rollers, etc. Dermal tissue is greatly influenced by temperature in permitting or diverting the blood to reach the surface of the skin. When skin is exposed to cold temperatures, the small arterioles in the dermis constrict, resulting in reduced blood flow, thereby protecting the core skin temperature.14 Cold therapy in the esthetic setting should be applied in short sessions and for no longer than 10 minutes at a time.
As with any esthetic treatment, caution should be taken, as there are contraindications to both hot and cold thermotherapy. Some contraindications and precautions include: obvious inflammation, stroke, broken skin, pharmacology, open wound, phlebitis, medications that cause skin interaction with heat, ischemia, decreased sensation, non-inflammatory edema, paralysis, heart failure, clotting disorders, recent hematoma, facial tissue grafting, facial burns, diabetes, Raynaud’s Syndrome, skin malignancy and cancer.
Health, Hydration and Happiness
Thermotherapy and the benefits of thermoregulatory applications have been proven to benefit many aspects of health for centuries. Utilizing these techniques in esthetic treatments by applying the alterations of thermotherapy and cryotherapy in the same session, will increase the health, hydration and vitality of the skin. Your ingenuity combined with these approaches will help you to create unique service options by using what nature has graciously supplied to us—water!
Erin Madigan-Fleck, NMD, CDT, LMC, LEI, has more than 35 years of experience in the aesthetic and natural health industry. She is a master esthetician, licensed esthetic instructor, and naturopathic medical physician with a private practice, Naturophoria, in Atlanta. She serves on the educational board and is a member of the Association for Applied Corneotherapy and is a member of The American Society for Nutrition and the American naturopathic Medical Association. She is the owner and founder of DermaEducationTV Post Graduate Esthetic Training and the Scientific Esthetics Symposium. She can be reached at: [email protected]