Biofreeze® is a popular over-the-counter pain reliever. While menthol (the active ingredient in Biofreeze) has been classified as a counterirritant providing pain relief, recent research has suggested the mechanism behind Biofreeze is related to the stimulation of cold receptors in the skin.
Dr. Robert Topp and his colleagues at Marquette University and the University of Louisville have spent several years researching the mechanisms behind Biofreeze in comparison to ice (Olive et al., 2010; Topp et al., 2011; Topp et al., 2011). Ice is commonly used immediately after injury to reduce pain and swelling because of its vasoconstrictive effect, thereby reducing blood flow to the area of application. This decrease in blood flow is thought to slow the tissue metabolism of the injured area, thus sparing healthy tissue and reducing swelling. Ice is thought to decrease pain through a counterirritant effect (the Gate Control theory) and subsequent increase in pain threshold, although ice is relatively painful at first application before numbness sets in.
Dr. Topp and his colleagues recently investigated the effects of 3.5% topical menthol (Biofreeze gel) to ice, as well as a combination of both, on blood flow and discomfort. 19 subjects had the treatments applied to their right forearm on different days: Biofreeze, Ice Bag, or Biofreeze + Ice. Blood flow was measured at the radial artery in the wrist using high-resolution ultrasound at 5 minute intervals after application for 20 minutes. The researchers also measured discomfort on a 10 point scale.
All 3 conditions significantly decreased blood flow over 15 minutes after application:
- Ice: 20% to 24% decrease
- Biofreeze: 17% to 24% decrease
- Biofreeze + Ice: 36% to 39% decrease
After 20 minutes, only the Biofreeze + Ice (-38%) and ice alone (-27%) treatments exhibited significant reductions in blood flow. Discomfort was significantly less using Biofreeze than in the 2 ice conditions throughout the 20 minute application.
Based on their findings, the researchers believe that menthol reduces blood flow through a spinal reflex, which may account for a rapid decrease in blood flow after application. They also noted the nervous system was quick to adapt to the menthol application, accounting for the short-lived (15 minute) reduction in blood flow. In contrast, ice requires 15 to 20 minutes to evoke a maximal effect on reducing blood flow. Interestingly, combining ice and Biofreeze resulted in the largest and most sustained decrease in blood flow.
Dr. Topp and his colleagues concluded that menthol and ice reduce blood flow through different mechanisms, and when combined, have an additive effect. The difference in discomfort between the initial application of ice and menthol also supports the theory of different mechanism behind their action.
The researchers concluded that menthol can be used immediately post-injury “to initiate reduction in blood flow, which can be enhanced when ice is added.” Furthermore, topical menthol produces less discomfort with application, which may provide more immediate pain relief after an acute injury compared to ice application. When ice is not immediately available, Biofreeze is an excellent choice to reduce pain and initiate vasoconstriction, which is indicated immediately after an acute injury.
Disclosure: This study was supported by Performance Health
REFERENCE: Topp R, Ledford ER, Jacks DE. 2013. Topical menthol, ice, peripheral blood flow, and perceived discomfort. J Athletic Train. 48(2):220-225.