<human>:  How do I clean a mattress that has been stained?
<bot>: Start by removing any debris such as pet hair and dirt from the mattress. Then use a vacuum cleaner to vacuum the mattress. Next, mix a solution of mild detergent, such as dishwashing detergent, in warm water and then using a clean cloth, apply the solution to the stained area and use a gentle circular motion to scrub. Finally, use a clean, wet cloth to rinse the detergent off the mattress and allow it to dry completely before using it.