There are several reasons that sneezing can sometimes cause back pain. They include:

• Sudden Spinal Compression: When you sneeze, your chest muscles contract and your spinal column is momentarily compressed. This sudden compression can strain your back muscles and spinal discs, especially if they are already weakened or strained from previous conditions.
• Pre-existing Back Conditions: If you have a pre-existing back condition such as a herniated disc, spinal stenosis, or degenerative disc disease, the force of a sneeze can exacerbate the condition and cause pain. The intense pressure from a sneeze can further push the disc material out of place, aggravating nerve pain.
• Muscle Strain: The forceful contraction of your body’s muscles during a sneeze can lead to muscle strain. If your back muscles are tight or weak, a sneeze can cause a sudden strain that results in pain.
• Spinal Instability: People with less stable spines due to conditions like osteoporosis or previous injuries may experience more significant shifts in their spine when sneezing, leading to pain.
• Irritation of Nerves: A sneeze can also momentarily increase the pressure within the spinal canal, potentially irritating spinal nerves. If a nerve is pinched or irritated, the added pressure from a sneeze can cause sharp or shooting pain.

It’s important to note that occasional back pain from sneezing is common and usually not a cause for concern. However, if you experience severe, persistent, or recurrent back pain when sneezing, it’s advisable to consult a healthcare professional to rule out any underlying conditions that may require treatment.