I have found that a dog's skin can be extremely sensitive. They can have reactions to cut grass, dirty water, shampoos, conditioners, doggie perfumes, bug bites, etc. The list is endless, just like it is for humans.
The other problem is that, people so often easily discount the problem. The dog is scratching and scratching and can barely rest because his or her skin is driving them mad. So don't ignore the problem!
Here is more information:
As explained in the the section on dietary intolerance, an adverse reaction to food most frequently affects the skin or digestive system. This is why skin and intestinal disease in their various forms are probably the commonest problems seen by veterinary surgeons.
In the dog this can vary from a low-grade itchiness, which many owners accept as normal for a dog to severe widespread inflammation with reddening, blisters, eruptions, weeping clear fluid or pus. The appearance, frequency and distribution of lesions (areas of damage) varies tremendously. In most dogs self-mutilation by scratching, licking, chewing and biting serve to aggravate the problem.
The cat tends to produce less dramatic symptoms. Scratching tends to be less but the cat will groom excessively. As the condition progresses the cat will become moth-eaten in appearance as bald patches appear. There will often be numerous tiny dry scabs all over the skin (known as military eczema).
Skin irritation tends to recur and become persistent and difficult to treat although some dogs tend to be affected only seasonally. Occasionally the problem will surface when the bitch comes in to season or has puppies. Some breeds are affected more than others (West Highland Terriers seem particularly prone) so there is clearly some genetic susceptibility.Diagnosis of skin disease can be extremely complicated and a mini-industry funded by pet insurance companies has grown in recent years. Dogs are frequently found to be "allergic" to many different outside factors such as fleas, house dust mites, wool, carpets, synthetic furnishings, cleaning materials, chemicals in the diet, foodstuffs. Veterinary immunologists insist however that true food allergy is present in less than 10 % of dogs that are tested.Many "allergies" are due to food intolerance rather than true allergy, the difference being that an allergy is characterised by involvement of the immune system whereas an intolerance is not. The clinical symptoms are the same.Treatment of skin irritation usually takes the form of anti-inflammatory drugs (steroids), antibiotics, de-sensitising regimes using vaccines tailored specifically to the individual dog.None of these approaches is likely to prove rewarding because they fail to tackle the true, underlying cause of the problem which is the build-up of toxins in the dog's system. It is often impossible to prevent the dog encountering those things to which it is allergic (grass, house dust etc.) but it is possible to treat the dog by changing the dog's system so that it does not over-react to its normal environment.Many cases of skin disease are due to an undiagnosed adverse reaction to food ingredients and a change of diet which eliminates the offending ingredients will be effective.Essential fatty acids (EFA) are important for maintaining healthy skin and there are many preparations on the market which are high in EFA’s e.g. Evening Primrose Oil, fish oils etc. These will be useful to supplement a diet which is deficient in EFA but a properly formulated diet will have adequate levels.