“Unwashed, used, and moist towels have the highest risk for skin infections.”
Dr. Peter Barratt
Initial Washroom Hygiene 
In a study conducted by the University of Arizona, it was found that 90% of bathroom towels were contaminated with coliform bacteria (bacteria present in faeces) and about 14% carried E. coli . Towels are prolific for breeding this sort of bacteria because they contain the moisture, warmth, and organic material that allow these bacteria to thrive, especially when they are hung in a steamy, dark bathroom with the door closed. This is why the average towel was found to be harboring 164,000 bacteria per square inch and to put that in perspective, that is 465x more than your toilet seat !
Whenever you dry yourself with a towel, you are depositing bacteria, viruses, and dead skin cells onto your towel providing food that bacteria like Coliform, E.coli, and MRSA need to grow. If your towel is not sufficiently dried before the next use, then this bacteria will cause a moldy smell that lingers in the fabric of your towel. This means that the next time you use this moldy towel it is transferring those germs back onto your skin increasing the chance of spreading acne . Although your own germs won’t make you sick, sharing towels will increase the risk of contracting a skin infection .
“Whilst harmful bacteria do not usually grow outside the human body, they can survive for considerable periods of time on damp towels etc. and sharing such items with an infected person may provide the opportunity for cross-infection.”
International Scientific Forum
"Bath and Toilet Hygiene in the Home"
The chief culprit in this regard, is your hand towel because it is used frequently by several people and has the least chance to dry before being used again. If people don’t wash their hands correctly before drying, then they are essentially depositing bacteria on your hand towel, where it will only multiply and fester.
This bacteria growth is worsened when you are cramming hand towels and other towels on the same bar because this not only inhibits drying but it also spreads bacteria from one towel to the other. This bacteria transfer typically occurs from your dirtier hand towel to other towels that are in contact with it.
“As long as it’s drying completely between use, there’s almost no chance of passing bacteria from one person to another”
Director of Clinical Microbiology, New York-Presbyterian and Columbia University Medical Center 
Based on this advice it is clear that towels should be hung up to dry with as much of their surface area exposed as possible, a criterion that traditional towel bars and hooks fail to meet. Whether it is double folding on a traditional bar or the overlapping folds of fabric hanging from a hook, moisture will be trapped making it easy for odorous bacteria to linger in the fibers of your towel. Not only does this increase the chances for cross-contamination but it also means you will have to launder your towels more frequently to avoid that damp, musty smell.
Susan Whittier suggests that you might be able to get away with laundering your bath towel only once a week if it is drying sufficiently between uses but advises that once it starts to smell to get it in the wash asap!
Since your bath towels are most likely not drying fully on your current towel rod or hook, this means that you should probably swap them out almost every other day.
Sound like too much hassle?
Instead, we recommend using the Airfold Towel Bar to open up every surface of your towel to airflow and keep your towel fresh for longer so that you can get back to your best self, your fresh self!