Objectives: To retrospectively collect data on patients with burn injury due to hot depilatory wax. To investigate the effect of varying microwave output power on wax temperature. To determine whether instructions provided by manufacturers allow safe domestic use.
Methods: Data from the RAH burns database was collected for patients with wax-induced burns between January 1991 and January 2010. Wax temperatures were tested in a pilot study (4 wax products heated in microwave with power outputs of 800 W, 900 W, and 1100 (W) and a definitive study (5 wax products, 3 of each, heated in microwave with power outputs of 800 W, 1000 W, and 1200 (W). A number of different heating regimens were employed and temperatures were recorded using an infrared thermometer.
Results: Twenty-one patients were studied. Mean age was 26.5 years. The majority of burns were superficial (33.3%) or partial thickness (25.8%). The right hand was most commonly affected (38.1%), the mean total body surface area was 1%. The pilot study revealed an increase in wax temperature with the number of times the wax was heated. During definitive wax temperature testing, the maximum wax temperature recorded was 108.5°C. Seventeen of 60 wax surface temperatures recorded exceeded 90°C, 9 exceeded 100°C. Ninety-three percent of the stirred wax temperatures showed an increase in wax temperature with an increase in microwave power output.
Conclusion: Microwave-heated hair-removal wax has the potential to reach unsafe temperatures and cause burn injury, even when manufacture's heating instructions are followed. Safe use in domestic setting requires improvements in instructions provided by the manufacturer.