My husband, 41 has a burning sensation on the bottom of his feet. What causes the burning? He saids " it feels like he's walking on fire"

Feet. Different things can be reason for that. Commonly could be due to Neuropathy-nerve problems which could be due to diabetes, nerves problems at the back. Also could be due to arthritis in the feet. Another possibility could be due to nerves damage/injury at the feet, to rule out any lumps on the feet. Better to see podiatris for detailed exam.