Smelly towels are not only unpleasant, but it is also very unhealthy.
Turns out the source of most smells in your absorbent fluffy towels is damp bacteria.
So there are a few simple rules of thumb to keep your towels from ever getting to that point.

Image By: Clean My Space Via YouTube
First, you will always want to hang your towels over a towel rail, or a shower rail.
Dont use a hook to hang towels on, because they will not dry on a hook.
If you already have smells going and you will need to strip your laundry.

Run a full cycle with just the vinegar.
Then you will do another hot cycle using 2 cups of baking soda.
