Allergy-related itchy skin

Author: Hannah Dyball
Published: Friday 23rd May 2014
Updated: Friday 30th May 2014

What is an allergy?

Itchy skin can be so intolerable that we scratch ourselves until we’re sore. For dogs, who don’t understand that scratching only exacerbates the problem, itchy skin is an unbearable condition that becomes difficult to manage. Itchy skin, or pruritus as it is medically known, is one of the most common reasons for pets to visit the vet, aside from gastrointestinal problems.

But while it is so common, there are many different reasons why a dog may suffer from it, meaning interventions do not always treat the cause. Itchy skin is triggered by a host of factors, including environmental, nutritional, allergic, parasitic, neurogenic and infectious. Because all of these factors relate to a negative or hypersensitive internal response to something, such as environmental causes relating to dust, pollen and mould (known as atopic allergies), and parasitic relating to the saliva of ticks and fleas, it is useful to think of them all as allergic triggers.

Allergy-induced itchy skin is particularly nasty because it can be lifelong, is difficult to diagnose, and even after diagnosis, it can be resistant to many forms of treatment. On a basic level, an allergy is defined as an over-reaction of the immune system to a particular substance, with the body responding as if it were facing a threat. This response will prompt numerous symptoms, from puffy eyes and runny noses to itchy and inflamed skin. One of the most common allergies in humans is hay fever, with the immune system over-reacting to the harmless inhalation of pollen particles. As dogs are susceptible to such an array of sensitivities, pinpointing which one is causing the itchy skin becomes difficult. There may be no way of treating the allergy per se, but if you know what’s behind it, keeping your dog away from the allergen in the future should help alleviate the skin complaint.

What types of allergy can my dog suffer from?

Atopic allergens are inhaled, many of which involve environmental substances we are exposed to every day. Pollen (from grass, weeds and trees), dander, dust and mould can all prompt an allergic response in your dog. Avoiding these triggers is sometimes neigh-on-impossible, especially during warm spring and summer months when our dogs are enjoying being outside. Keeping your dog inside when the pollen count is particularly high i.e. during late evening and early morning, as well as when the lawn is being mown, will reduce your dog’s exposure to these potentially harmful allergens. While respiratory problems are the most frequently experienced in human hay fever sufferers, itchy skin is the most common symptom in dogs.

If a particular allergen is identified, your veterinarian may suggest allergy shots, which can be administered weekly to help enhance the immune system’s tolerance to a particular substance. Regular shots of the allergen can make your dog less sensitive to it, the downside being it can take a good few months to notice any improvement. Pinpointing an allergen is usually done by a blood or skin test but, depending on where the itchy skin is and your dog’s other symptoms, your vet should be able to advise the most likely cause for its condition.

Contact allergies are a lot less common, but they still affect a significant number of animals. A contact allergy relates to a particular surface your dog comes into contact with that triggers an acute immune response. This usually shows through a rash that most often appears on the feet, stomach, muzzle and elbows. Whether it’s an allergy to carpet, fabric, plastic, wood (i.e. cedar), surface cleaners or lawn chemicals, your dog will need help bypassing these areas in the future. If your dog’s sleeping quarters are outside, steering clear of cedar wood dog houses and treated decking is a good idea, and tile or linoleum floors (as opposed to carpets) are the best option for indoor dogs. Cotton is safer than wool and alternative bedding fabrics for animals with allergies.

If your animal suffers from a contact allergy, it will probably experience red, inflamed and itchy skin at the site of contact, which it will scratch and bite at, exacerbating the cycle. This behaviour will leave affected areas raw and painful from being constantly aggravated. The areas might be hairless from where repetitive scratching has worn the coat away, with raised scales and welts that are kept continually moist from excessive licking. If you are not careful, broken skin can become infected very quickly and this is definitely important to avoid. If you notice an area of skin that is bald, red or inflamed, take your dog straight along to the vet.

You may have heard about sweet itch, a condition affecting equines that is caused by an immune hypersensitivity to the saliva of the Culicoides midge. In response to foreign saliva, a horse’s immune system over-produces histamine, which, in turn, leads to itchy and inflamed skin. A horse will rub and bite at these areas so much so that the coat and skin is often worn away, leaving room for secondary infection. In a similar way, fleas can be particularly bothersome to dogs with sensitivity to their saliva. An over-active immune system will cause uncomfortable itching and scratching as it responds to the ‘threat,’ with just one flea being all that’s needed.

The hind legs and tail end are the areas that are most likely to be affected by parasitic allergens. A dog will rub itself raw for relief from the irritation in these areas, often stripping out hair or rubbing away its coat in the process. Symptoms of parasitic allergic response include redness of the skin (erythema), bumps (papules) and scabbing.

The best method of defense is strict flea control, involving the use of regular treatments on your dog and in your home. VioVet stocks a range of effective flea, tick, lice and mite treatments and spot-ons, as well as insecticidal sprays for your home. Although these will not cure the allergy, by eradicating flea allergens from the domestic setting you are protecting your animals from their potentially harmful effects.

Ten percent of all dogs with allergies will have them as a result of something they’ve eaten. Itchy skin is very often the result of a food allergy, with the worst offending food source being corn. Corn is a staple ingredient in many commercial dog feeds and is often used as a filler, included to bulk up the product rather than providing a nutritional benefit. Other than corn, common food allergens include chicken, beef, dairy, wheat, egg and soy. A dog with a food allergy is going to exhibit classic signs of skin irritation; it may scratch its face, feet, legs, flanks and anal area, whilst its stools may be softer and more frequent. Ear infections are also common symptoms of food allergy. Food intolerances are different altogether and often result in more severe symptoms.

Avoiding low quality diets that are high in carbohydrates and cheap fillers is a good idea if you can’t determine the food that’s causing the reaction. Isolating a particular allergen is difficult as your dog may be reacting to several different things at once. Obviously, avoiding diets that contain a specific ingredient is the way forward when it comes to treating, or managing, a food allergy. Higher quality diets with a better nutritional balance to include fibres and proteins are best for all dogs, regardless of whether they have allergies or not. They may initially cost more to buy but they should go a lot further, with your dog needing to consume significantly less than it would of a commercial feed. Whatever diet you do give your dog, ensure it is fresh and unspoiled; do not feed kibble that is dusty or past its best as this will cause problems.

How do I manage my dog's condition?

While treating allergies, whether they are atopic, contact, parasitic or food-related, is not always easy, there are remedies on the market and with prescription to help manage the symptoms of itchy skin. Avoiding known allergens is the most effective measure, but identifying these is fairly hit-and-miss. All types of allergic dermatitis can be soothed to some extent with medicated baths, creams and topical sprays, although future recurrences of itchy skin may be less affected by these if your dog develops resistance to them. Medicated shampoos can be used on dogs with itchy skin if rinsed with cold water (hot water will only aggravate the skin), while too much bathing can have a detrimental effect by over-drying the skin and coat. Oatmeal shampoos are generally thought of as the best remedy for bathing pets as they do not strip the skin of its natural oils but help to moisturise and soothe. Oatmeal can be used on its own to alleviate symptoms of itchy skin - simply soak oats (porridge oats, just like the ones we eat for breakfast) in water and then coat the mixture over your dog, focusing on the itchy areas in particular. Leave this on for a while before rinsing off with cold water. Quick, easy and some would say, highly effective!

Along with allergy shots that are injected and work in a similar way to vaccinations, steroids can be given to control the symptoms of allergies in dogs. Unlike allergy shots, the side-effects of steroids, or corticosteroids as they are known medically, are much more serious. All effective drugs have their drawbacks and, being highly effective over a short space of time, steroids have more than their fair share of these. The thing to decide is whether the prospect of alleviating the effects of your dog’s allergy to its skin and general well-being outweighs your concern for potential side-effects. While the short-term use of steroids is thought relatively safe, using them for a long period isn’t recommended.

Side-effects of steroid use range from weight gain, fluid retention and increased blood pressure, to more severe incidences of diabetes, cataracts of the eyes, muscle weakness, bone thinning and growth suppression. That said, the positive effects of steroid use are just as impressive, hence why so many dog owners opt to use them. First of all, steroids get to work quickly, usually within 24 hours, and help to relieve inflamed and irritated skin before it progresses to infection. If your dog is suffering a flare up, corticosteroids will reduce allergy-related inflammation, thereby stopping the animal from traumatising affected areas through scratching, biting and licking.

Besides steroids, antihistamines are often prescribed by veterinarians to relieve allergy-induced itchy skin. These work by blocking the release of histamine (hence 'anti'-histamine) in order to minimise inflammation of the skin. Antihistamines are generally considered safer than steroids although they do have some adverse effects such as drowsiness and lethargy. The long-term use of antihistamines can have a very detrimental impact on a dog’s lifestyle and well-being because of this, which is something to bear in mind when considering this course of treatment. On the whole, these drugs can be effective against itchy skin, working in the same way that antihistamines work in human allergy-sufferers. However, not all animals respond to antihistamines and some will show no signs of improvement on this treatment.

Some pet owners swear by natural, herbal remedies in tackling itchy skin, although the effectiveness of these is disputed. Besides oatmeal (shampoos, conditioners and oatmeal itself) which has already been mentioned, there are several other natural remedies that have showed positive results in soothing canine dermatitis. Astringents that dry and tighten the skin and thus reduce swelling and redness work well on itchy, inflamed and/or broken skin. Witch hazel extract is an astringent that appears in many a human and animal skin treatment because of its fast-healing properties. It can bring immediate relief to moderate swellings, helping to reduce inflammation and soothing discomfort, while it is easy enough to get hold off.

Aloe vera and calendula are also beneficial natural remedies for the skin that are known for their healing properties amongst other things, promoting skin recovery when combined together. Peppermint, lavender and chamomile are also well known for their accelerated healing properties and their assistance in fighting harmful bacteria; these can be topically applied to help treat and soothe skin itchiness and swelling. Omega-3 and fish oil supplements are also associated with good skin health and can be used to restore the condition of the dermis. Avocado oil is again, another herbal remedy believed to contain beneficial agents for skin and coat.

If you suspect allergy-induced dermatitis in your pet because of a visible sign or a behavioural change, the first step is to get him seen by your veterinarian for a proper diagnosis. It may be that an allergy is the supposed cause, but pinpointing the specific allergen involved in the hypersensitive response takes a little longer to identify. Skin and blood tests may be taken to dismiss other potential causes and your veterinarian will ask you a number of questions; if your dog suffers with itchy skin at certain times of the year, it is very likely that it is induced by an allergy. Environmental (atopic) and parasitic allergens are more prevalent in spring and Summer months when the pollen count is high and when summer fleas and midges are more numerous. It may be that your dog is allergic to a certain food such as corn or poultry and needs this removing from its diet. Your veterinarian will be able to give the best advice on what to avoid and what to use to treat and manage the condition most effectively. Discuss all your treatment options with him before deciding on the course of action for your pet, and consider all potential side-effects. Even if your dog does not respond to a certain treatment, persevere. With so many remedies on the market, there is bound to be something that works!