If you suddenly develop lower back pain, then you'll probably associate it with carrying heavy objects, being on your feet all day, or sitting at your desk for prolonged periods of time. While these are common reasons for lower back pain, there are other, less common causes. Here are three surprising reasons for your lower back pain and what you can do about them: Allergies Whether you have food allergies or if you're allergic to cats, you may have an increased risk for developing lower back pain.