Aside from the numerous dermatological uses and effects of Salicylic Acid, it is also an effective topical pain relief agent:

Topical acetylsalicylic, salicylic acid and indomethacin suppress pain from experimental tissue acidosis in human skin

1995; Steen KH1, Reeh PW, Kreysel HW.
https://www.ncbi.nlm.nih.gov/pubmed/8657434