Most people first notice that their dog is allergic to something via digestive upset or a dermatological reaction. These dog skin allergies can be as obvious as clumps of hair falling out, or as moderate as slightly increasing scratching.
A trip to the veterinarian is necessary if your dog has a skin problem. Dermatological ailments in dogs can be caused by a wide variety of problems, and some, such as parasites, require specialized treatments that only your vet can provide. If allergies is the diagnosis, then you can begin to treat your dog.
Problems on the skin do not necessarily come from outside the dog. Allergic reactions to foods often manifest on the outside of the body, though some allergens are topical, such as fleas or rubbing against something that creates an allergic reaction. Food and pests such as fleas are by far the most common sources of canine allergic reactions, though.
Removing everything that the dog is likely to be allergic to from his or her environment and diet is generally the first step in treating him or her. If, after this purge of potential allergens, the problem resolves itself, then the possible allergens can be reintroduced one by one until the culprit is found. Switching the dog to a low-allergen food is a very important part of the process, because wheat and grain allergies are common in dogs, and these products are often found in commercial foods.
Removing fleas from your dog's environment is also important. Many dogs are allergic to flea bites, and while being treated with a preventative will prevent infestation, if there are fleas in the environment, they can bite the dog often enough to trigger a reaction. Treatments should still be used, but cleaning the home and treating it for fleas may also be required with sensitive dogs.
Air particulates such as dust and mites can elicit allergic reactions in some dogs. While usually this reaction is respiratory, it is worth eliminating them as much as possible from the environment of an allergic dog to see if they are the problem. Air purifiers are good, if you have or are willing to buy one, but cleaning is essential. This should include vacuuming and dusting with a dust-trapping cloth, at the very least.
Treatment like this doesn't always work for dogs who are reacting to something extremely common. Your vet can talk to you about prescribing medication if this is the case. However, if you still don't know what the problem is, consider going through the list of potential allergens a few more times with your vet, in case you missed anything. Removing the allergen itself is always better than medicating your dog.
Dog skin allergies can be itchy, or even painful for the dog, as well as causing disfigurement such as hair falling out. Treatment is essential, and while removing allergens from the dog's environment is the best ultimate treatment, your vet may give you some kind of soothing cream or antihistamines in order to remove discomfort while you are figuring out what he or she is reacting to. Be diligent in using them, in order to alleviate your pet's discomfort as much as possible.