Paraffin Baths and How They Work

Paraffin baths are a form of conduction heat transfer and work well for arthritis pain. Superficial heating methods like hot water baths, hot packs, electrical heating pads and warm compresses usually do not heat deep tissues, including muscles, because the subcutaneous layer of fat beneath the skin surface acts as a thermal insulator and inhibits heat transfer. Also an increased cutaneous blood flow from superficial heating causes a cooling reaction as it removes the heat that is applied externally.

The transfer of heat is classified into 3 general types of heat transfer - conduction, convection, conversion.

Conductive heating like paraffin baths is defined as heat transfer from one point to another without noticeable movement in the conducting medium. Typically, direct contact takes place between the heat source and the target tissues. Heat such as hot water baths, hot packs, electrical heating pads and warm compresses are conductive heat.

Heat methods are categorized by the primary heat transfer modes as follows:

Conduction - Hot packs, paraffin baths

Convection - Fluidotherapy, hydrotherapy, moist air

Convective heating is produced by movement of the transferring heating medium, usually either air or fluid. Methods for providing convective superficial heat include fluidotherapy, whirlpool, moist air baths, and hot air baths.

Conversion - Radiant heat

Conversion heating involves heat transfer by conversion of energy from one energy form like light, or sound to another which is heat. The heat is produced by heat lamps or radiant light bakers, where heat is transferred when the conveying medium of light energy is converted to heat energy at the skin surface.

Conductive heating is usually a simple method that can be used at home.. The disadvantages of this method include potential burns, difficulty with application to regions exhibiting abnormalities and the skin-drying effect with the exception of paraffin or water media.

Forms of hot packs for home include the Kenny pack (vigorous short-term stimulation/heating), rubber hot water bottle, and electric heating pad. Heat transfer is enhanced if the pad is moist or if the heated part is wrapped in moist material. The complications of electric heating pad include shock hazard if the device is not insulated properly and burns if the patient falls asleep lying on the pad. Heat output increases over time until equilibrium is achieved. Keep in mind that heat may be sufficiently analgesic to produce burns.

Paraffin bath is another form of conductive heating. Paraffin baths are particularly useful for contractures due to rheumatoid arthritis, burns, and progressive systemic sclerosis (scleroderma). Paraffin usually is applied to the hands, arms, and feet. Paraffin wax is melted and mixed with liquid paraffin. For therapeutic use, the paraffin bath is maintained at the melting point of 51.7-54.4°C in a thermostatically controlled insulated container. The 2 application methods include (1) the dip method and (2) immersion.

The dip method

The hand or foot is placed in the liquid paraffin bath and withdrawn when a thin layer of warm solid paraffin forms, becomes adherent, and covers the skin. The dipping procedure is repeated until a thick paraffin glove is formed. The heat can be retained by wrapping with towels for 20 minutes; then, the cool solid paraffin glove is peeled away and the paraffin is recycled. The dip method is a mild heat application because only a limited amount of heat is available for transfer to the skin.

Immersion

Alternatively, the body part is immersed in the paraffin bath for 20-30 minutes. The immersion method transfers heat not only from the solid paraffin block but also from the liquid paraffin bath itself. The heat transfer rate from the liquid paraffin bath to the skin is slowed as the solid paraffin glove provides a poor thermal conductor. This modality represents a vigorous heat application, causing a significant increase in skin tissue temperature, up to 46°C, with a marked temperature decrease in the subcutaneous tissue. Water at the same temperature applied by the same method would be intolerable because of the high specific heat and thermal conductivity.

Paraffin baths or fluidotherapy should not be used in open wounds that are either clean or infected.