Laundry soap is obviously laundry soap.Even in a baggie. It smells like laundry soap , and it looks like laundry soap. It does not look like Coke or Heroin. Relax. We have taken laundry soap this way for years. It is in our checked bag, and since checked bags are dog sniffed, a dog knows the difference between soap and drugs. If one carried the baggie of " laundry soap" in their carry on it would look rather suspicious, I mean, it is just soap.
I have a small bottle of Tylenol that I never throw out, I just buy the big bottles of the pills and take what I need in the small bottle.
I also have to take a prescription med that I get in large amounts, but , I can peel the label off the big bottle and apply it to a smaller bottle and take a smaller amount.I use the proper label and it is a proper pharmacy bottle so it is perfectly legal. Just go to your pharmacy and explain the situation and they may give you a smaller bottle, they won't give you another label though, you must have the original.