Have you ever applied a topical gel (or spray or roll-on applicator for that matter) called Biofreeze?
If not, it's probably best summarized as being like a super-potent, prescription-strength (it's not a prescription product, for the record, however it's only available at the offices and clinics of chiropractors, physical therapists and related healthcare professionals who routinely work with intramuscular, bone and joint injuries.
You can't get it at pharmacies or other specialty shops - health included - unless a healthcare professional works on-staff, full-time for the organization if more retail/sales oriented as opposed to therapeutic.