What it looks like
Scratching or licking that has no obvious trigger, redness in the folds, the armpits, the groin or between the toes, flaking, a coat that thins in patches, and skin that reacts to a new shampoo, a new bed or a change of season. Some dogs are simply built this way. Many have a cause that can be found.
Causes worth ruling out
Parasites, especially fleas, are the first thing any vet will check, because a single bite can set off weeks of itching in a sensitive dog. Environmental allergies to pollens, dust mites or moulds are common and often seasonal. Food sensitivities exist but are less common than the internet suggests. Contact reactions to washing products, floor cleaners and fragrances happen too. A vet can work through these in order; guessing tends to waste months.
What gentle care does
It removes the avoidable irritants. A fragrance-free wash formulated for dog skin, rinsed thoroughly, gives the skin fewer things to react to. Bathing less often, drying properly and keeping the coat brushed and free of debris all reduce the background load. For a dog with a known allergy, regular gentle washing can also help remove allergens from the coat.
What it does not do
No cosmetic product treats an allergy, an infection or a parasite. If a dog has red, broken, weeping or smelly skin, or scratches enough to disturb its sleep, gentle care is not the answer on its own. See a vet, and only then choose the products to use alongside whatever they advise.
Introducing anything new
Change one thing at a time. Try a new product on a small area first and wait a day. Keep a note of when flare-ups happen. Patterns, more than products, are what eventually explain a sensitive dog.