But the people cleaning thousands of oiled sea birds washed up along the Pembrokeshire coastline have no hesitation in declaring that Fairy Liquid, its best-known brand, washes feathers whiter than any other product.
It is good at getting out the oil and at being rinsed out, leaving the feathers nicely fluffed. And, the RSPCA says, it is kind to the hands of those cleaning the birds.
"Yes, they do donate it to us, but we use it because we've found it's the best," said Colin Booty, the Society's officer in charge of the RSPCA's new emergency bird hospital, which opens today in Milford Haven, west Wales.
Last night more than 2,100 birds had been rescued since the super tanker Sea Empress ran aground 12 days earlier.
A small army of volunteers is helping RSPCA inspectors rescue the birds. Most birds picked up alive have survived.
RSPCA overrun, page 5
Photograph: Tim CuffReuse content