Yes, you can use a Dettol laundry cleanser with a fabric softener. Dettol laundry cleanser has antibacterial properties and when used as a laundry cleaner it is very effective at killing off any germs or bacteria on the cloth. However, make sure you add the cleanser before the wash cycle. Also, ensure you add only 2 capfuls of the cleanser together with the fabric softener and detergent.