Powders won't dissolve completely when using cold/normal water.
So you run a maintenance wash monthly with nothing to dissolve it. There is other points here.
How much powder are you using ?
What brand of detergent powder are you using ?
Also, for some reason I felt a slight itchiness when washing with powder. Hence recently shifted to Ariel liquid. Though LG recommends sticking with powder, experience is proving something else.
So this isn't easy to figure out. But it has more to do with how you use the washer and the detergent than the detergent. If that makes any sense.
eg. Overdosing or over loading. Either way will leave unused detergent residue in your clothes. That will cause itch.
How you used the machine or detergent and not the detergent
per se.
A third factor is improper detergent for a FL can also be the culprit. A detergent for a TL generates excess suds with less water of FL means it won't rinse out as well leaving residue in the clothes. Because it was formulated to be used with more water.
People do seem to correlate the two though. There isn't any proof for it.
One major detergent manufacturer told us flatly, "You have more chance of winning the lottery three weeks running than getting a skin rash from powder or tabs, the amazing amount of testing and hoops we have to jump through just to get a formula to market ensure that".
In short, the right detergent and used properly won't cause itch.
It causes smells particularly if you wash regularly at low temperatures. Low means less than 60 degrees.
Then you need specialised cleaning products like Whirlpool's
Affresh to remove this smelly residue from the drum and you need to be regular with it.
No need for Affresh if you stick with powders.
Affresh is no longer available on amazon so only Bosch's
cleaner is left. You need to use that whole 200gms for one use. See the price
I do use liquid detergent but only for washing a load of microfiber cloths. Powder is bad for micro fiber. That is my only use for liquid detergent.