Foot spa massagers have become a popular way to relax and soothe tired feet, but there are some potential side effects to be aware of before using one.One common side effect is that the massage can cause skin irritation. If you experience any skin redness, swelling, or discomfort after using a foot spa massager, stop using it and consult your doctor.Another potential side effect is dehydration. The massage can cause your feet to sweat, which can lead to dehydration if you don't drink enough fluids. Be sure to drink plenty of water after using a foot spa massager to stay hydrated.Finally, if you have any preexisting medical conditions, consult your doctor before using a foot spa massager. It's possible that the massage could aggravate those conditions.