In general, server burns of significant partial or full thickness burns, destroy the sensory nerves in the skin, so while very serious, are not always that painful. Pain can and does occur around the edges of the burn (3rd degree), in such cases, pain relief with medication such as morphine is preferable. In these cases, topical applications of medications containing lidocaine have very limited value and would have to be scrubbed away for definitive treatment.
Full and partial burns are life threatening, requiring specialized care such as debriding, surgical incision of the severely burn skin to allow for swelling, specialized medications for infection control, skin grafting and other medical procedures.
Burns, even 1st degree to the face, groin, circumvential around limbs and large surface areas are serious and require rapid and specialized medical care.
Pete