Scratching, licking, chewing, rubbing, and biting are all tell-tale signs you have an itchy dog and one of the most frequent and often most frustrating reasons for a trip to the vet
While there is a long list of reasons that a dog may develop itchy skin, this blog is going to give you a broad overview of the most common causes of an itchy dog and how your vet might go about diagnosing and treating these.
The most common causes of itching in dogs are parasites, infections and allergies and your vet is going to ask you a range of questions to try to narrow down the likelihood of each of the potential causes into one of these areas. You’ll be asked questions like:
- Whereabouts are they itchy and how often are they itching?
- Where have you noticed lesions and did you notice these before or after your dog became itchy?
- When did your last have flea treatment and what type of product did you use?
- Is anyone else in the family itchy or have skin lesions?
- When did this start? How old was your dog when this first started?
- Is it happening all year round or just in a particular season?
- Have you been anywhere different with your dog lately?
- Have you changed their diet lately?
- They may also ask about previous treatments, such as corticosteroids, antibiotics, flea treatment and shampoos and how effective you feel these may have been.
Here’s a brief summary of the most likely causes of itching, signs you may see and how your vet will go about diagnosing and treating them.
Fleas
The first thing your vet is going to want to rule out is parasites. Unsurprisingly these are the most common cause of itching. These little rascals can often be spotted in a quick search of the tail base and the groin area, which is where they most love to hang out. You may see the fleas themselves or the gritty, black flea poo they leave behind. And often other family members are aware of their presence! If we strongly suspect fleas, but can’t find them, brushing with a flea comb or even running a wet cotton wool swab can sometimes pick up evidence of their presence.
There are many effective flea treatments available these days and often it is wise to treat both the dog and the house.
Sarcoptic mange
Sarcoptic mange (scabies) is caused by the sarcoptes mite, which burrows into the dog’s skin causing severe itching and hair loss in a fairly characteristic pattern over the ears, elbows, hocks and chest area. They are highly contagious and can also infect people.
The best way to find these mites is through skin scrapings, but because they burrow deep they can be hard to find. If we have a strong index of suspicion for sarcoptes, but can’t find them, we will do a therapeutic trial and treat your dog with an appropriate parasiticide and assess their response.
Bacterial infections
Bacterial skin infections, also known as pyoderma, are very common in dogs and have many presentations. They are usually caused by Staphylococcus pseudintermedius, a bug that is normally resident on healthy skin. When something disrupts the normal healthy skin barrier this bug proliferates and sets up an infection.
Hot spots are a common bacterial infection that tend to start in the skin folds in very hairy breeds. They are particularly common after swimming or washing if the area is not properly dried. Hot spots can progress very quickly into a severe infection.
Fungal infections
Fungal infections are usually caused by a bug called Malassezia pachydermatitis, which just like Staph bacteria is present on healthy skin, but will take advantage of any disruption to the skin barrier to set up an infection. Fungal infections often start in folds of skin before spreading further, usually have a characteristic ‘yeasty’ smell and affected skin will be quite greasy.
Diagnosing and treating infections
With antibiotic resistance now becoming a serious issue it is really important for your vet to get the diagnosis and treatment of any bacterial or fungal infection right. This requires cytology which is where we take an impression smear or tape strip of an infected site, or a swab from an infected ear, and look for bacteria and fungi under the microscope. This allows us to make a decision on medication options, but in some cases we may also send samples off to the lab for culture and sensitivity to confirm the exact bug and which medications will work. This is particularly important with chronic skin and ear infections.
With both bacterial and fungal infections we try to use topical medications, such as medicated shampoos, as much as possible. Where infections are deep seated then we may need to use systemic antibiotics or antifungal medications and these may need to be given for a longer period of time.
What causes skin infections?
As bacteria and fungi live on normal skin, something needs to happen to the skin’s defence mechanisms to allow them to set up an actual infection. This is known as a secondary infection because it happens secondary to some other inciting factor. Most commonly in dogs the skin barrier is weakened by either a contact allergy, atopic dermatitis or a food allergy.
Contact allergies
These are allergies caused by something your dog has physically come into contact with, usually a plant, although I have seen dogs with allergies to sheepskin blankets and concrete! The most common plants that cause contact allergies are grasses such as Kikuyu and Wandering Dew. These will cause itchy, red skin in the areas that have come into contact with the allergen, such as the paws, belly and groin.
Treatment involves settling down the inflammation, using some of the medications discussed below, and avoiding the allergen in future.
Atopic dermatitis
Atopic dermatitis (Atopy) is a genetic predisposition to developing allergies to environmental allergens such as pollens, dust mites and mold spores. It is a complex disease and one that is lifelong. The breeds most commonly affected are Golden Retrievers, Bulldogs, Dalmations, and most terrier breeds, but even mixed breed dogs can be affected.
Symptoms of atopy typically begin to appear at a young age, usually between 6 months and 3 years of age. Atopic dogs present with scratching, licking, chewing and/or rubbing of either their face, ears, perianal area, belly, under their armpits and their paws or any combination of these! At the very start you often can’t see any lesions, but all that itching damages the skin surface, bacteria and/or fungi invade and they progress to having very red, inflamed skin which may be either dry and crusty or oily and there is often significant hair loss.
There is unfortunately no single test that can be used to diagnose atopy - it is what we call a diagnosis of exclusion. So, your vet will need to rule out the other likely causes of your dogs itching and scratching before feeling confident to give this diagnosis.
Treatment involves controlling the current itch with medications, eliminating secondary infections, and then making a long-term plan for lifelong management.
Medications that help control the itch
For some dogs with very mild atopy shampooing with a medicated shampoo may be enough, but even these dogs may have allergic flare ups, which can often be seasonal, and require something stronger on occasion.
Corticosteroids
Steriods have been our traditional ‘go to’ medication for allergic dogs and they are highly effective at controlling the itch. But, they come with potential short and long term side effects. In up to 50% of dogs steriods cause increased appetite, thirst and urination and sometimes these side effects can be very difficult to live with! Longer term, dogs who have been on steroids are also more likely to develop diabetes and Cushings disease.
Apoquel
Apoquel (oclacitinib) is a newer generation drug with a better safety profile than steroids, although it cannot be used in dogs under 12 months and those with serious infections. It comes in pill form and is initially given twice a day for 2 weeks before tapering down to once a day for maintenance therapy. The major downside of this drug is its cost, but is very effective.
Cytopoint
Cytopoint is an injection that can control itching for 4-8 weeks. It is a very different form of treatment as it is a monoclonal antibody. Allergic dogs have very high levels of a specific protein which causes their itch and a monoclonal antibody will work on just that protein to neutralise it.
This is also a more expensive treatment than steroids, but can be used in dogs of all ages and those with existing infections.
Essential Fatty Acids
Although EFAs will not treat itch they can be effective at improving the integrity of the skin barrier and so are worthwhile considering using as an adjunct therapy in atopic dogs.
Allergy testing and immunotherapy
Allergy testing allows us to identify exactly what in the environment your dog is allergic to. This can be done either via a blood test or intradermal skin testing, which is where an area of skin is clipped up and a small amount of each potential allergen is introduced under the skin and then assessed for signs of a reaction.
Allergy testing is not diagnostic for atopy, as even normal dogs will react to some allergens but not have signs of clinical disease, but in a dog with clinically diagnosed AD it can be useful to know what the dog is allergic to and the extent of allergies. Your dog may only be allergic to one or two things which may potentially be avoided in the environment, especially if they are highly seasonal, or may be allergic to things like house dust mites, which will be harder to control.
The results of allergy testing can be used for allergen specific immunotherapy. This is a process of desensitisation using a tailored protocol of injections over a period of about a year. The injections contain the offending allergens and the idea is to desensitise the immune system over time so that it no long over reacts. Studies have shown that around two-thirds to three-quarters of dogs respond well. The protocol is used under the supervision of a veterinary dermatologist as it often requires tweaks in the volume or frequency of injections, but pet owners give the injections themselves at home.
The downside of immunotherapy is its expense but it is the only real potential ‘cure’ we have for atopic dogs. Given atopy is a life long condition it is worth considering, especially in large breed dogs where the costs of antibiotics and anti-itch medications can quickly add up.
Food Allergies
Food allergies can develop at any stage of life, even if your dog has been fed the same food for its whole life. Pet food companies have done a good job of marketing grains as the major cause of food allergies, but research shows this is not the case and most food allergies are caused by chicken, beef and lamb, with wheat a distant fourth place.
Animals with food allergies can show very much the same pattern of lesion as those with atopy. This can make diagnosis tricky. In addition, about 30-50% of dogs have both atopy and food allergy. The likelihood of a food allergy being part of the problem is raised if the itching continues all year round and/or if there are gastrointestinal symptoms as well.
Elimination diets are the best way to diagnose a food allergy. This involves feeding a specific veterinary therapeutic diet for 8-12 weeks to see if symptoms resolve. If they do, then you rechallenge the dog with the original diet (called a provocation trial) and if the skin flares again you have confirmation of a food allergy. You can then find longer term diet that will be suitable for your pet.
When to see a specialist
As you can see, getting to the bottom of skin conditions can be tricky. It can take several vet visits to definitively diagnose a problem and to get the treatment plan right for your dog. One of the keys to success here can be to make sure you always see the same vet, as it can be really hard for a vet that has never seen your dog before to pick up a long and complicated case history and be able to give you good advice in the space of a 15 minute consultation.
If your dog’s skin problem has become complex and ongoing, your general practice vet may recommend seeing a specialist veterinary dermatologist. There are skin specialists throughout the country and although they may cost more at the outset, if you have a dog with a skin condition that is proving hard to diagnose or difficult to manage then they can be well worth the extra cost. As many skin conditions, such as atopy, are lifelong expert treatment from a specialist can end up being cheaper in the long term than constant vet visits and endless courses of antibiotics.
More information is coming
We’re going to be putting together further informative articles for you which go into many of these areas in much greater depth so make sure you are following our social media or signed up to our newsletter to be notified about these as they are published.
