Broadly speaking, the reasons a dog can itch can be categorised as infection, parasitic or allergic. This doesn’t cover all diseases but the most common.
Infection can be bacterial or fungal. Bacterial infection is usually secondary to another condition making the dog itchy, but can occasionally be a primary condition. Antibiotics are used to treat bacterial skin infection, regardless of cause, and sometimes long courses are needed. If possible, it is sensible to use topical treatments first such as antibacterial shampoos and mousses, to try and limit resistance problems but we do understand that this isn’t practical in all situations and deep infections do require tablets. Sometimes we may want to take swabs to send to the laboratory to see which bacteria are causing the problem and which specific antibiotics are needed.
Sometimes dogs can get an overgrowth of yeast on their skin and this can cause greasy and itchy areas. Again, this usually happens secondary to another skin problem. Again topical treatment is the first line choice in these cases and often shampoos will target the bacteria and yeast. Your dog will continue to be itchy whatever the underlying cause if they have an untreated bacterial or fungal infection.
The most common parasites we encounter are fleas and they can be doubly problematic as some dogs are allergic to the flea saliva. This is why for any itchy dog we very strongly recommend regular flea control for all dogs and cats in the household. The sarcoptes mite is a burrowing skin mite that causes a very intense itch and the Demodex mite is a mite that is present on the skin of all animals but can proliferate on the skin of young pups or immune compromised animals to cause a problem. Often fleas or flea dirt are visible to the naked eye but the best way to check for parasites is by taking coat brushings, skin scrapes and hair plucks and having a look under the microscope. The sarcoptes mite can be hard to find though due to it burrowing deep within the skin. There are several good anti-parasitic medications on the market now that will kill these mites and other medications may be added in to control itch and treat any concurrent infection.
Allergic skin disease in the dog is very common. Dogs can be allergic to many things and often there are multiple allergens involved. Grasses, pollens, house dust mites and mites that live in the dust of dry food are all common culprits.
Dogs can also be allergic to one or more food ingredients. In an ideal world we would rule out a food allergy or intolerance first. This can be achieved by feeding a dog a food with a protein content that it has never encountered before or a hydrolysed diet (where the protein molecules are manipulated so that they do not illicit an immune response). We can source these foods for you. This food will be fed for six to twelve weeks and all other treats cut out. If there is an improvement in symptoms then a recurrence of symptoms when the dog is fed its normal diet again will point to a food allergy or intolerance. The dog can then have their diet changed long term. If improved but still itchy there may be other allergies involved as well.
Allergy or atopy, as it is referred to, is really diagnosed by the exclusion of other possibilities. There are a number criteria that help lead to diagnosis such as the itching starting between
six months and three years old, some breeds such as Westies, Labradors, German Shepherds, Boxers and Bull terriers are predisposed, and the parts of the body usually affected are chin, face, ears, feet, “armpits” and belly.
There are blood tests available that help to identify possible allergens. These can help as sometimes it is possible to take steps to reduce exposure to the offending allergens which is the ideal way to manage this condition. It also allows for a vaccine to be made for these allergens in the hope of desensitising your dog to them over a course of injections which usually results in monthly injections. We find this can work really well with limited side effects in approximately 50% of cases. It is best to wait until your dog is over eighteen months before taking blood so they have built up sufficient antibodies to test.
Traditionally steroids were used to manage the symptoms of allergy. The advantages being they are usually very effective and affordable. They do however have side effects including increasing your dog’s thirst and hunger and your dog may pant more. Steroids can have longer term effects such as muscle wasting, lethargy and predisposing to secondary infections. Therefore we try to use steroids only in the short term but, if we do use longer courses, we can tailor the dose to hopefully give maximum effect but minimum side effects.
The most common tablet we give now to control itching contains a drug called oclacitinib. This helps by blocking part of the itch pathway with less widespread side effects than steroids. This drug is licensed in dogs over 12 months old and is usually given twice daily for two weeks then once daily. We would not use this drug in dogs that have had previous cancers or chemotherapy as it can potentially lower a dog’s white blood cell count. The function of white blood cells is to fight infection so we may monitor white blood cell counts with screening blood tests if we feel appropriate. We have found this drug has had a really positive effect on many patients who are now leading a happy itch free life.
We now also have an injection in our armoury in the fight against itch. It is a very safe medication and mimics the dog’s own immune system in neutralising one of the main proteins that sends the itch signals to the brain. Injections are usually monthly and are really effective in the majority of patients.
It is important to note though that none of the above treatments will be effective alone in the face of infection or parasitic infection which is why we must control these factors as well.
There are no licensed antihistamine drugs for dogs but we may discuss the use of them as an adjunctive treatment with you if we feel appropriate. Another helpful adjunct is the addition of essential fatty acids. A lot of good commercial diets already have good levels of fatty acids but they can also come in capsule form. They help maintain the skins protective barrier and will often improve coat quality. We wouldn’t normally advocate shampooing a dog but as well as the anti-bacterial and anti-fungal properties of shampoo we may recommend, shampooing may actually help in removing allergen from the skin and coat, and can help with general skin health.
In short an allergic dog may be managed with a combination of diet, anti-itch medication, antihistamine, a nutritional supplement and shampooing. This will be tailored to the individual and may change over the seasons if allergy is seasonal or over time if symptoms change. This is not a curable condition but can be managed long term very successfully in most cases, with some peaks and troughs. We are always here to help and advise and talk you through the options.