Just like you, your dog will sometimes have an itch that he needs to scratch. However, extreme itching and scratching is a symptom of an underlying problem. There are multiple reasons for itchiness including allergies, mites, bacterial and fungal infections, and ear problems.
Allergies
Allergies are perhaps the most common cause of itchiness in dogs, and there are many types of allergies that may impact your dog including allergic contact dermatitis, atopic dermatitis (atopy), flea allergy dermatitis, and food hypersensitivity (flea allergies).
Allergic Contact Dermatitis
Allergic contact dermatitis is a form of allergic reaction that usually occurs due to prolonged contact with an offending agent such as a household deodorizer, rubber chew toy, floor cleaner, detergent or plastic dish. Signs of allergic contact dermatitis include itchiness, redness and skin lesions in the areas of your dog's body that come into contact with the allergic agent. As the condition progresses, the impacted skin may become darkened and/or thickened. To treat allergic contact dermatitis, your vet will generally give you a soothing hypoallergenic shampoo to be used on your dog to wash off the allergens. Your vet may also prescribe topical steroids or a short-term course of oral steroids to reduce the inflammation and itchiness. Really the only means by which allergic contact dermatitis can be effectively prevented from reoccurring is to remove the offending agent from your dog's environment.
Atopic Dermatitis (Atopy)
Atopic dermatitis, also called atopy, is a hypersensitivity reaction to environmental allergens your dog inhales or absorbs through his skin. Examples of typical allergens from the environment are grasses, pollens, molds, animal dander and dust mites. Dogs typically develop this condition between the ages of 1 and 3. However, atopy can develop in dogs of any age.
In contrast to allergic contact dermatitis in which only the portion of your dog's body that comes into contact with the allergen is generally impacted, with atopy many areas on your dog's body tend to be itchy and irritated. Most commonly, the irritation will be on your dog's face, ears, paws, armpits, and sides of the abdomen. These areas might also have lesions caused by your dog's scratching and chewing. In some cases, your dog may also have hair loss, thickened skin, darkened skin, saliva stains on the fur and skin, and crusting. Secondary infections such as bacterial and yeast infections can develop from the ongoing skin trauma.
Diagnosis of this condition is based on your dog's history and the symptoms described above. As for determining the cause, allergy testing can be helpful but sometimes results in false responses. Skin biopsies are also sometimes used to help determine the cause of your dog's atopy.
Treatment is focused on managing and controlling symptoms. The best way to do this is to remove the allergen from your dog's environment if this is possible. For example, your house or whatever interior environment your dog spends time in should be kept meticulously clean and free of dust. HEPA filters can also be used to remove particles from the air, and lowering the humidity levels can also aid in removing mold and dust mites.
If it is not possible to remove or reduce the allergens from your dog's environment, your vet may suggest allergen specific immunotherapy in which your dog will be given an allergy vaccine injection composed specifically for him and his allergies. Your dog will get an initial series of injections and then booster injections over the course of his life. Approximately 60% to 80% of dogs will improve with the vaccine, but results may not be seen for 3 to 6 months.
Another method to control symptoms is to give your dog periodic baths using anti-itch shampoos. These shampoos are generally quite effective. Some veterinarians may also recommend giving your dog anti-histamines and steroids to relieve itchiness. Both anti-histamines and steroids can be given in either oral or topical form. However, oral steroids have numerous potential side effects so they should not be used as a long-term solution.
Flea Allergy Dermatitis
Flea allergy dermatitis (FAD) is a condition in which your dog is hypersensitive to the saliva of fleas. FAD can be triggered by only one bite from a flea, and it will cause your dog to be extremely itchy and likely to have inflamed skin covered in tiny red bumps. Generally, the inflamed skin will be on back of your dog's thighs, the sides and bottom of his abdomen, and along his back.
If your dog has these symptoms and you can find fleas or flea dirt on him, this will likely lead your vet to make a diagnosis of flea allergy dermatitis. However, because this allergy can be caused by one little flea bite, sometimes there are not enough - or even any fleas or flea dirt currently present on your dog - to make the diagnosis obvious. In this case, your vet may attempt to treat to your dog's itchiness and rash with flea control products. If your dog responds to this treatment, then the vet will know that your dog has flea allergy dermatitis.
Food Hypersensitivity (Food Allergies)
A food allergy, as the name implies, is when your dog is allergic to a particular food or food additive in his diet. Protein sources, such as chicken and beef, are one of the most common allergens. Also seen somewhat frequently are allergies to certain grains such as rice.
Food allergies usually develop quite early in your dog's life, generally before your dog is one-year old. Food allergy symptoms include vomiting, diarrhea, excessive gas, skin itchiness, poor coat quality, foul smelling skin, inflamed skin and/or ear infections. The gastrointestinal signs (vomiting, excessive gas and diarrhea) are present in approximately 25% of food allergy cases. Food allergies, unlike many environmental allergies that may come and go with different seasons, will not wax and wane.
The only true way to diagnose a food allergy is to perform food trials. A food trial consists of changing your dog's food to either a limited ingredient food or a hypo-allergic food. Limited ingredient foods are generally composed of one carbohydrate source and one protein source. The protein will be a novel protein meaning a protein that your dog has likely not yet been exposed to. Examples of novel proteins include venison, duck, fish, and kangaroo. Limited ingredient diets used to be available only by prescription through your vet. Recently, however, several commercial dog food companies such as Natural Balance and Wellness have developed limited ingredient foods available without a prescription. Hypoallergenic diets are generally designed to have very easily and thoroughly digestible proteins. The theory is that if the protein can be broken-down into small enough pieces within your dog's digestive tract, your dog's body will not be able to mount an allergic reaction to the protein. Hill's Prescription Diet Canine z/d® Ultra Allergen Free is an example of commonly used hypoallergenic dog food.
The problem with food trials is that they are "trials" in the true sense of the word - your vet can only make an educated guess as to which food ingredient your dog is actually allergic to. It can also take at least 12 to 14 weeks for a food trial to begin to yield any positive results. During a food trial, it is essential that you do not allow your dog to have ANY flavor-containing chew, treat, toy, medication, or supplement. The food trial will not be valid if your dog is given anything besides the trial food. At the end of the food trial period, if your dog's symptoms abate your vet will likely suggest that you continue feeding your dog the food used in the food trial. If symptoms have not abated, your vet may decide to start a new trial with a different food.
Overall, allergies can take time to diagnose and to treat. As a responsible dog owner, you need to strictly follow your vet's recommended treatment plan. Most allergic treatment failures are due to the owner's failure to comply exactly with the vet's prescribed treatment plan. Of course, there are also veterinary dermatologists available for you to consult with about your dog's problem. These specialized veterinarians have had additional training in the area of skin diseases and can bring a wealth of knowledge to your dog's case.
Mites
Mites are another relatively frequent cause of itchiness. The two most common mites to cause itchy skin conditions are demodectic and sarcoptes (scabies). Symptoms of scabies include scratching, hair loss, crusty or scabby sores, and irritated, inflamed skin usually on your dog's ankles, belly, ears, elbows, and the underside of his mouth. In some cases, if you look closely, you can see the tunnels that the mites have burrowed into your dog's skin. The tunnels will look like very thin and scaly lines up and down the infected area of your dog's skin. For more on scabies including prevention, diagnosis, and treatment, click here. Demodectic mange may be localized or generalized. Localized demodectic mange can cause your dog to be itchy around his paws (called pododermatitis) or around his mouth, eyelids and lips. The itchiness is generally accompanied by hair loss in the impacted areas. Generalized demodectic mange will cause your dog to be itchy and have hair loss over most of his body.
Bacterial & Fungal Infections
A bacterial infection or fungal infection, such as malassezia dermatitis (essentially a yeast infection), can also cause your dog to be itchy. These infections can occur secondary to allergies and skin parasites. Bacteria and yeast thrive in warm and moist areas such as in between your dog's paw pads and the skin folds on many dogs' faces, necks, and tails. Generally, if your dog has a bacterial or fungal infection, in addition to being itchy your dog will have red sores in the affected areas.
Ear Problems
If your dog constantly scratches his ear(s) or rubs his (ear)s on the ground, his itchiness may be caused by an ear infection or ear mites. Ear infections all need to be treated by a vet as they can progress to become quite serious. To learn more about ear infections click here. Ear mites are tiny parasites that can make a home on your dog's ears and feed off your dog's ear wax and oil. If your dog has ear mites, you will likely notice a dry, black-colored discharge in his impacted ear(s) that looks similar to coffee grounds. Sometimes you will also be able to see the actual mites which look like tiny white flakes.
For more information on each of the conditions listed here, including flea prevention and flea prevention products
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