Sensitive skin turns washing a dog into a process of elimination. You try one shampoo, the scratching carries on or gets worse, you try another, and after a year there are five part-used bottles under the sink and no clear idea which of them was the problem. The useful moment is not finding a formula that suits — it is the moment after that, when you stop guessing and start buying properly.

This is the 5 litre bottle from Johnson's professional shampoo range, and it is the size that follows the guessing rather than starting it. Johnson's describe it as an extra-mild formula intended for dogs with sensitive skin, meant to leave the coat clean and fresh and to help avoid skin problems. That one sentence is the entirety of what has been published to us about it.

• 5LTR bottle
• Johnson's describe it as an extra-mild formula
• Intended for dogs with sensitive skin
• Sold within Johnson's professional shampoo range
• Meant to leave the coat clean and fresh

What Johnson's have not published. There is no ingredient list, no dilution ratio and no pH figure for this shampoo anywhere in what Johnson's have supplied, and "hypo-allergen" is not a term a product has to be tested against before it can go on a bottle. That matters more here than on an ordinary shampoo, because the whole reason someone reaches for this one is that they are trying to work out what their dog reacts to. A dog whose skin is already broken, weeping or smelly needs a vet rather than a different wash.

Who it's for: groomers, breeders and multi-dog households who already know this formula suits the dogs they wash, and want the container that costs least per bath rather than the one that fits on a bathroom shelf.