Pain is a curious thing - it's obviously unpleasant, but it's what stimulates people to seek remedies. Topical pain relief refers to getting rid of pain by applying something directly to the area affected, rather than taking something internally, like a pain killer. In order to think about how herbs can do this, it's worth considering how pain is generated in the first place.
Throughout our bodies, and particularly in our skin, there are tiny sensors called nociceptors, which are stimulated by the presence of certain substances. These are most likely noxious chemicals, like poisons from microbes, or messenger chemicals (i.e. cytokines) produced by the body itself during tissue damage and inflammation. The activation of nociceptors sends messages through our peripheral nervous system to the central nervous system, to register the presence of the damage being caused. Our perception of this information is pain.
In conditions like rheumatoid arthritis (RA), the presence of ongoind inflammation in the tissues is continuously acitivating the pain receptors, giving the sufferer ongoing discomfort. Pain relief can thus be achieved in two ways: reverse the damage by removing the problem or disrupt the messaging somehow. Generally speaking, holistic approaches aim to deal with the underlying causes of a condition. However, as with RA, the exact cause is not always known or not easily undone. Herbs that promote healing of local structures, or encourage the body to tackle the source of a problem are obviously encouraged. Herbs known to promote healing in the skin or soft tissues, such as Calendula, Arnica, and Symphytum, are going to contribute to pain relief for this reason. Similarly, herbs that promote local circulation will also provide some topical pain relief, including Zingiber, Xanthoxylum and Cinnamomum.
Many mainstream topical pain relief agents are instead focussed on disrupting the generation, and therefore the processing, of pain itself, rather than removing the cause. Local non-steroidal anti-inflammatories work in this way by preventing the production of the cytokines messengers, which the body naturally makes as part of the inflammatory process. Many medicinals plants also create substances that can block inflammation in a similar way, and there are more and more studies, such as the one by Su et al. (2015) in Scientific Reports, which confirm there efficacy. However, it should be noted that this study was a trial conducted on rats (those poor creatures!), and the authors neglected to mention whether the extracts (see image above) were administered topically or systemically. That said, many topical pain relief preparations will include herbs that work in this way, like Boswellia, Commophora and Lavandula. Realistically, this kind of herbal medicine is not often as 'strong' as the conventional products available. However, they are gentle and inexpensive, with no well-known side-effects.
You watch a short video about one very nice topical pain relief product here.