Question from Leona Poppleton:
my dog has skin allergies and so gets very dry skin and sometimes scabs that look quite painful is there anything that I can get or do to help this?
Answer: Scabby Skin
Hi Leona, thanks for your question about your dog’s skin. Allergies with skin symptoms are pretty common in dogs, so I’ll briefly discuss allergic disease, then go on to some of the many different treatment options.
What are skin allergies?
The phrase “skin allergies” refers to the itching, scratching and sore skin that allergic dogs get. However, it doesn’t have to be caused by something on the skin – e.g. food allergies (although quite rare in dogs) can lead to skin symptoms – so “allergic skin disease” is a better term.
Essentially what is happening is that the dog’s immune system misidentifies a harmless substance as a dangerous threat, and tries to attack it, causing soreness and itching. Allergic reactions may be triggered by a wide range of substances such as pollen, certain foods, fleas, mites, plants or even some washing powders. In a large number of cases, there’s no specific “allergy” involved, but the dog has a disease called Atopy (or Atopic Dermatitis), where the immune system reacts abnormally to a wide range of different stimuli. Atopy is partially genetic, and is more common in some breeds (e.g. West Highland White Terriers).
How is it diagnosed?
It is important to get allergic skin disease properly diagnosed by your vet because there are many contributing factors and different underlying problems. As a result, diagnosis can be long and exasperating! In addition, diagnosing Atopy requires ruling out all other possible causes.
1) Initially, its vital to make sure that there aren’t any parasites (especially fleas!) on the dog – this is a LOT harder than most people think, and usually requires treatment of the affected dog, all other pets in the house, and the house itself. (A side note here – there are a lot of over-the-counter products available for treating fleas: some work, some don’t work, and some are very dangerous if not used correctly. I would strongly advise talking to your vet for advice, particularly as the most effective treatments are prescription-only medicines, some of which will also act over time to treat the environment as well as killing adult fleas).
2) The next step is to make sure there aren’t any skin infections that could be contributing to the symptoms, or mites burrowing into the skin. This may require skin scrapes to remove a layer of skin (it really doesn’t hurt!) and tape-strip tests to check for yeasts or bacteria.
3) There are a number of allergy tests available – these mostly use blood samples; intradermal tests (injection of test substances into the skin) may be more reliable, but they are expensive and difficult to perform.
4) To rule in or out food allergies, a controlled food trial is essential. This can be done with truly novel food sources, but in general it is more effective and practical to use a hypoallergenic diet from your vet. These diets are formulated so that the proteins are broken down so small that the immune system can’t recognise it. In a food trial, the dog is fed ONLY the controlled diet (no treats or snacks!) for a number of weeks. If the symptoms resolve, you reintroduce the original diet one item at a time, to determine what’s causing the allergy.
But why does it make my dog itch so much?
Itching is what’s called a “summative, threshold” experience. This means that there is a threshold level, below which itching won’t be felt. Anything that stimulates an itch (“pruritic”) response such as a flea bite, an allergy, or a skin infection, raises the level of “itch” until it breaks this threshold and the dog feels itchy. In most allergic dogs, several different factors combine to make the itching overpowering. Unfortunately, actually scratching makes things worse – this is called the “itch/scratch cycle”.
What are the scabs I can sometimes see?
Scabs generally mean one of three things:
1) Flea bites
2) Skin infection
3) MOST COMMONLY – self-inflicted skin damage caused by scratching. The skin is sore because it’s been scratched, and it’s been scratched because its sore etc etc… Scratching also damages the skin and allows infection to become established, which makes the itching worse.
What can I do about it?
The bad news is that most allergies cannot be cured, only managed. However, with good management, most cases of allergic skin disease can be fully controlled the vast majority of the time. There are a number of classes of treatment, which I’ll deal with in turn; however, many cases will require multiple overlapping treatments, so it is essential that you work with your vet to put together a management programme.
1) Disease modifying treatments
These attempt to reduce the underlying allergic response. The most effective are licensed immune-modifying drugs such as ciclosporin*, which when used long term reduces the allergic response. There is great hope for immunotherapy, where the immune system is gradually taught to tolerate certain allergic substances; this must be made up by a lab specifically for your dog’s allergies. Sometimes an allergy can be “cured” by this route, but it is more usually used to reduce the dog’s sensitivity.
2) Relieving symptoms
These act specifically to reduce the sensation of “itch”. There are three main drugs used for this. Firstly, antihistamines; these are not licensed for use in dogs and may have noticeable side effects, but a vet can legally prescribe them under the cascade if necessary. My experience is that they aren’t very reliable in dogs, but may be useful in some cases. There is also a new drug called oclacitinib which works purely to suppress a dog’s itch sensation. Finally, there are steroids. These reduce inflammation, mildly suppress the immune system and are very, very effective at reducing itching. They’re also inexpensive; however, if used long term, they have a wide range of side effects. They’re often best used as a “rescue” treatment, although steroid creams and sprays that can be applied directly to the sore spots on the skin have fewer side effects.
3) Reducing other sources of itching
This category would include products such as antibiotics for skin infections and antifungals for yeast infections (many of which are available as medicated shampoos), and parasite treatments for fleas and mites.
4) Reinforcing the skin barrier
This is a relatively new area, but seems to be a really useful in some cases or in addition to other treatments. There are soothing and hydrating shampoos which work to remove allergic substances from the coat and soothe the skin; as well as oatmeal shampoos which seem to have an anti-itching effect. Finally, there are the ω-3 fatty acids which appear to help many itchy patients; they may be in the diet (particularly in “skin” or “dermatology” diets), added to food as a supplement, or used as a topical spray or spot-on.
Overall, you and your vet need to find the combination of treatments that suit your dog. Managing the allergic pet is a big task, but I hope this has helped, and that you can keep your dog comfortable!
David Harris BVSc MRCVS
* PS – you may notice I’m using generic drug names not brand names in this article. This is because, for legal reasons, I’m not permitted to name specific brands in a blog like this. If you want to know more, check out the government’s Veterinary Medicines Directorate website.