I have used the
Natural chemistry de flea pet shampoo and still have some/most of the bottle left. I always make a solution with shampoos to use on my dogs so I didn't use it full strength. I am uncertain how well the shampoo worked because when mine encountered fleas playing in a leaf pile near the edge of the woods, I did multiple things at once to eliminate them, and haven't used that shampoo in many months. It did no damage for the brief time that I used it, however.
I have heard also that Dawn works, but then again, it is my understanding that "any" shampoo will kill fleas if allowed to remain on the dog in contact with them for 10 minutes, which some flea shampoos say to do anyway. I would probably
not use Dawn dishwashing liquid to bathe my dogs because I tried Dawn when it first came out years ago and after only using it only a couple times found that it tore my skin up!!!
I kept my gentle dish detergent and just added a de-greaser...which is supposedly where Dawn excels...and de-greasers are not as common anymore.
I have heard that Dawn is more gentle now, but my experience soured me, unfortunately, and if it pulled that much oil out of my skin that fast, I'd be really hesitant to use it on my babies, or use it with my bare hands again.
I doubt this helps you in any way, but since I do still have the shampoo, and had no bad experience with it before, I would be "okay" with using it again. Just my opinion...