An outdoor doormat can harbor everything from allergens to dirt to rotting leaves and even insects, so regular cleaning is a must. While care varies slightly depending on the material, in general, it’s quite easy. Shake out the doormat weekly. Once per month, you need to do a bit of a deeper clean, vacuuming the mat. Seasonally, rinse the mat off with a garden hose, using a tiny bit of mild dish soap for any stubborn spots.