Have you ever wondered: "Do any of those creams, gels or patches on that huge aisle at the local drug store actually work?" Well, the research shows that they do work for minor aches and pains, and are good alternatives to oral pain medications, such as Tylenol (acetaminophen) or Motrin (ibuprofen). The next question is how do they work?
Understanding the Basics of Pain
There are a few types of receptors in your skin that are responsible for detecting pain and sensation. One set of receptors, called nociceptors, are responsible for detecting painful stimuli. Usually, the stimuli have to hit a certain intensity threshold to activate these receptors and let the body know it is experiencing a stimulus that it should recognize as pain. There are secondary receptors in the skin that are activated at a much lower level of sensation. These receptors can detect pressure, temperature and even chemical stimuli to help your body understand its environment. However, all of these different types of receptors can interact with each other to determine the final signal that is sent to the brain. In other words, stimuli from temperature and chemicals from a region of the body can reduce or amplify the primary pain signals being sent to the brain from that same part of the body.
How do These Gels, Creams and Patches Actually Reduce Pain?
There are so many creams, gels and patches on the market, it is difficult to review how each of the different ingredients works. However, there are a few common ways that the main ingredients in many of these products work. For example, Methyl Salicylate is an active ingredient in products such as Icy Hot, Salonpas or Tiger Rub. Its primary function is to act as a mild irritant to the skin as well as increase the skin temperature. As a result of applying a cream or patch with this ingredient, the chemical irritation and temperature change will activate the secondary set of receptors mentioned above. The signal from these receptors can interfere with the pain signals coming from the primary pain receptors. Therefore the brain perceives a reduction in pain as the signals from the pain receptors are disrupted by the signals from the secondary receptors. Capsaicin would be another example of an ingredient that works by counterirritant.
Additionally, Menthol is an active ingredient in products such as Biofreeze or Bengay. It's primary function is to give a cooling sensation to the skin. Although the mechanism is slightly different, the cooling effect activates the secondary temperature receptors and causes the same interference with the pain signals coming from the primary pain receptors to the brain. Camphor would be another example of an ingredient that works by cooling sensation.
Do You Want a Combo?
Most of these creams and gels come in combination form, combining Methyl Salicylate, Menthol and/or Camphor. In can be quite confusing, as the brand name may be the same, but as a combo, it may be labeled as "extra strength" or "ultra strength" for example. These products may also include topical lidocaine which can act to temporarily numb the skin in the injured area to aid with pain control.
As a side note, methyl salicylate is in the same family as Aspirin and should be avoided in those who have an aspirin allergy. Additionally, Camphor can be toxic if ingested and care should be taken around children.
Sources: Feucht CL et al, Analgesics and anti-inflammatory medications in sports: use and abuse. Pediatr Clin North Am. 2010 Jun;57(3):751-74.