When aches and pains set in, many people turn to over-the-counter (OTC) topical pain relievers, available as patches, creams, gels, foams, and even roll-ons, sticks, and sprays. Often filling multiple shelves in drugstores, these products go by such names as Aspercreme, Salonpas, IcyHot, Capzasin, Zostrix, Flexall, Biofreeze, and, of course, Bengay. They’re also available as store brands, as well as by prescription (though the main focus of this article is on OTC products).
Applying medication to the skin is referred to as transdermal drug delivery, as opposed to the oral route of swallowing a pill. In the case of topical pain relievers, the medication passes through the dermis into the deep underlying tissue, where most of its effects occur.
Transdermal delivery of pain-relieving substances goes back millennia. The Papyrus Ebers, an ancient Egyptian document on drugs and prescriptions from 1500 BCE, describes numerous topical treatments, including application of frankincense (an aromatic tree resin) to relieve headaches. In ancient China, transdermal patches, of sorts, were used in the form of herb-containing plasters applied to the skin.
Topical medications have some advantages: For example, compared to oral dosing, they generally allow for controlled delivery of a drug, with less absorption into the bloodstream, thereby limiting systemic (body-wide) effects and reducing the risk of adverse side effects. They may be an especially good option for people with localized pain who have difficulty swallowing pills or have health conditions (such as gastritis) that preclude them from taking certain oral pain relievers.
How well OTC topical pain products work—for conditions ranging from arthritis, simple back pain, stiff necks, strains and sprains, and muscle soreness after exercise to shingles pain and diabetic neuropathy—is debatable, however. Some studies have noted benefits, but the degree of relief may vary depending on the ingredient (not all medications are absorbed well through the skin), its concentration, how much is actually absorbed, how deep the pain is, and other factors. The products are not sufficient for many kinds of pain, and the effect is temporary at best. A placebo effect—the expectation that something will work—may also factor into any perceived benefits.
Still, topical medications are worth considering for conservative pain management, depending on the level and type of pain, before resorting to oral pain relievers (including ibuprofen and especially opioids), steroid injections, or other therapies that have more side effects and risks.
What’s in them
Here’s a brief look at four common ingredients, found alone or in combination in OTC topical pain relievers.
Capsaicin. This extract of chili peppers causes a hot sensation on the skin. Considered a “counterirritant,” it’s thought to reduce pain through a variety of mechanisms, including stimulating and then desensitizing specific nerve fibers, which, by reducing levels of the neurotransmitter “substance P,” interrupts the transmission of pain signals in nerves. Possible side effects include skin redness, burning, and stinging. OTC capsaicin is usually found in a 1% or lower concentration, which may be too weak to have significant effects. (A high concentration of 8% topical capsaicin is available by prescription, approved by the FDA for postherpetic neuralgia, the pain that can persist long after an outbreak of shingles.) If you want to try a capsaicin product, apply it to only a small area first to see if you can tolerate the sensation.
Menthol. Opposite to capsaicin’s heat, menthol, which is derived from mint oil and is also considered a counterirritant, creates a sensation of coolness that may counter pain by acting on nerve fibers. A few small studies suggest that menthol may provide relief from local musculoskeletal pain, sports injuries, and neuropathy. For example, a study in the International Journal of Sports Physical Therapy in 2012 found that applying a menthol gel to sore biceps muscles was significantly better than ice at relieving delayed onset muscle soreness resulting from exercise. Products with menthol (at concentrations greater than 3%) as a single ingredient or in combination with methyl salicylate (greater than 10%; see “salicylates” below) can cause burns, sometimes second- and third-degree burns, the FDA has warned.
Salicylates (methyl salicylate and trolamine salicylate). It’s thought that these aspirin-related ingredients relieve pain like other counterirritants by both stimulating and desensitizing nerves in the skin. Salicylates, which belong in the category of nonsteroidal anti-inflammatory drugs (NSAIDs), can also be metabolized in the deeper skin layers, resulting in some anti-inflammatory activity. If you’re taking aspirin or prescription medication that affects blood clotting, talk with your doctor before using topical salicylates, as they can increase bleeding risk.
Lidocaine. This is an anesthetic, an ingredient that numbs the skin, thus dulling pain. Adverse effects from topical lidocaine include mild skin irritation. People sensitive to other anesthetics, such as ropivacaine or bupivacaine (used, for example, in dental injections), should avoid topical lidocaine. And those who are taking a drug for heart arrhythmias should speak with their doctor before using it, since there is a low risk of arrhythmias when topical lidocaine is absorbed into the blood. (A prescription lidocaine patch is approved by the FDA for nerve pain associated with shingles, similar to prescription capsaicin, and is also used off-label for other types of pain.)
Comparing NSAIDs: Topical vs. Oral
Long-term use of oral NSAIDs has well-known adverse effects, including gastrointestinal irritation and bleeding and an increased risk of heart attacks and stroke. Are topical NSAIDs a safer option?
If you want to try a topical OTC pain reliever, you may need to sample different ones to find which, if any, work best for you. Follow the directions on the package, which include not using products on skin that’s irritated or has an open wound, and using them in specified amounts and for a specified time (more is not necessarily better and increases the risk of side effects).
Don’t apply a tight wrapping or combine them with heat (as in a heating pad), as these actions can increase absorption of the medication or cause burns; some products shouldn’t be combined with cold (as in ice packs), either. In particular, the numbing action created by lidocaine reduces the ability to feel the heat or cold sensation and thus increases the risk of burns or skin damage. If you develop redness or irritation, stop using the product.
If pain does not improve or worsens, talk with your health care provider—you may be a candidate for a prescription topical medication (as discussed in the inset above) or other pain management treatment.
Jeanine Barone contributed to this article.
This article first appeared in the UC Berkeley Wellness Letter.
Also see Can You MELT Away Pain—and More?
Published June 22, 2020