A towel is damp, warm and covered in skin cells — ideal for bacteria. What matters more than frequency is that it dries fully between uses.
The short answer
3–4 uses
When to wash sooner
Wash it now if
- it smells musty
- it has not fully dried since last time
- someone has been ill
What to do between washes
Hang it spread out, not folded over a rail. A folded towel never dries through and that is what causes the smell.
How to wash them
Hot occasionally to kill bacteria, no fabric softener — it coats the loops and destroys absorbency.