Atopy is not a disease; it is a predisposition to develop an allergic condition. In the dog/cat, this allergic condition usually manifests through the skin, this is called atopic dermatitis.
This skin disease can occur in animals with impaired skin barrier function and a hereditary hypersensitivity to harmless environmental allergens (such as house dust mites, tree and grass pollen and dander from other animal species). The allergens enter the skin more easily due to the disrupted skin barrier and trigger inflammatory skin reactions and itching. As the dog starts scratching, the skin becomes irritated and damaged, exacerbating the inflammation of the skin.
Also, in dogs with atopic dermatitis, the balance between the skin and the bacteria and yeasts normally found on it in small numbers is often disturbed. This can cause this so-called microbial flora to multiply and worsen the inflammation of the skin. This phenomenon is called microbial dermatitis. As a result, the condition of the skin deteriorates even further. In some of the animals with atopic dermatitis, food allergens also seem to be able to worsen the symptoms. Finally, the severity of the complaints is strongly influenced by several other factors, e.g., temperature, humidity, hormonal fluctuations and stress.
Because so many different factors contribute to skin inflammation and itching, symptoms can vary greatly. Every animal has an itch threshold. All factors contribute to itching to some extent. The sum of all those factors determines whether the itching exceeds the itch threshold. The itch threshold is not always the same, e.g., it is often lower at night than during the day. Therefore, atopic animals tend to be itchier at night.
Over time, the various factors that contribute to itching are not always the same. For example, environmental allergens are present only a limited part of the time (in the case of pollen grains), weather conditions change and the dog sometimes goes swimming. As a result, the itch sometimes exceeds the itch threshold, and sometimes not. As a result, atopic animals often have highly variable symptoms. Usually, complaints are worse in summer, even if animals are allergic to allergens that are present all year round, such as house dust mites. This is because in summer many other factors are often present to the maximum extent: heat, humidity and swimming. The skin is the barrier between the outside world and the body.
The skin's main functions include keeping harmful organisms and substances out and keeping moisture in. Normal skin can do this just fine because the skin cells are, as it were glued together, like the bricks and mortar of a wall.
In animals with atopic dermatitis, the skin barrier is disrupted because, among other things, the composition of the fats in the sealant layer is different. As a result, the skin becomes porous, so to speak, with all its consequences. Every animal has a small number of bacteria and yeasts on its skin. These so-called micro-organisms feel good in places where it is warm and moist: in the nose and around the mouth, under the tail and between the toes.
Healthy skin ensures that the number of micro-organisms is contained. Moreover, such healthy skin has a good skin barrier, which prevents bacteria and yeasts from doing harm. In allergic animals, the defense against the microflora of the skin is disturbed. This allows these micro-organisms to multiply and grow to large numbers, this is called microbial overgrowth. Moreover, because their skin barrier does not function properly, the bacteria, yeasts and the toxins they produce (toxins) can easily enter and cause inflammation on site: microbial dermatitis.
In 75% of dogs with atopic dermatitis, the first symptoms become apparent between the first and third year of life. It is rare for symptoms to appear at an age younger than 6 months. Atopic dermatitis is more common in certain breeds than others, for example the German Shepherd, Shar-Pei, Terriers, Shih-Tzu, Labrador retriever, Golden Retriever, Boxer, French Bulldog, English Bulldog and American Bulldog. The main symptom is itching. Furthermore, the allergy itself mainly causes redness and scaling of the skin. The symptoms can get worse by scratching, rubbing, biting and licking, eventually causing bald patches and elephant skin. If microbial dermatitis is also present, small bumps and crusts will form. Sometimes there is also more severe inflammation with swelling of the skin and bloody effusions and pus may be seen.
Skin problems are usually found on the head (especially around the muzzle and eyes), in the armpits, groin, on the belly and on the paws. Very many atopic dogs have ear infection as their main complaint. A small proportion of atopic dogs also have hay fever symptoms such as sneezing and eye discharge.
The complaints may or may not be seasonal, depending on the allergens to which the dog is hypersensitive. Also, the severity of the symptoms varies under the influence of a variety of factors such as temperature and humidity and internal conditions of the dog (stress, hormone fluctuations).
Determining whether a dog has atopic dermatitis is not easy; a complete range of examinations must be carried out before this diagnosis can be made. It is important that this is done very carefully, because the consequences are huge: a dog with atopic dermatitis will need a lifetime of treatment and extra care. For atopic dermatitis to be diagnosed, several conditions must be met: First, the nature of the skin problems must fit this allergy. In addition, the role of infectious causes and other allergies (such as food allergy and flea allergy) must be clear.
Once it has become clear that the dog has atopic dermatitis, further allergy testing can be done. A skin test and blood tests can then try to show which allergens the dog is hypersensitive to. No allergy test provides one hundred per cent clarity. Therefore, it makes sense to compare the results of both allergy tests. A negative result does not necessarily mean that there is no allergy. It only indicates that there are no antibodies against the tested environmental allergens at that time.
A skin test (intradermal test) can only be done on a part of the skin that is not inflamed. First (usually on the chest wall) a piece of fur of about ten by fifteen is shaved away. At this spot, a small amount of allergen solution is injected into the skin in a fixed sequence each time.
Exactly which allergens are tested depends on the allergens the dog encounters. The total number of allergens is usually between 20 and 24. 2 control solutions are always tested along with the test: a positive and a negative control to see if the skin responds well to the test. Once all the allergens have been injected, the test should take effect for about 10 minutes. During this time, the dog should not scratch or bite the test area. If it is cold, he should not go outside.
After this, the test can be read. If there is swelling at the injection site of a particular allergen, the dog is allergic to it. The swelling is always compared with the reactions seen in the positive and negative controls to draw the right conclusion. Finally, the positive reactions and the positive controls are treated with an itch-relieving ointment. Skin test injections are not very painful: by using a small needle and preferably allowing the test fluid to come to room temperature first, most dogs experience the pricks as irritating rather than painful. It is therefore almost never necessary to put a dog under anaesthesia for this test.
The blood shows whether the body has reacted to certain allergens by producing antibodies. For this blood test (serum test), some blood is taken and sent to a specialized laboratory. This laboratory tests a fixed panel of allergens (Northern European panel), which includes mites, pollen grains as well as dander from other animals.
Once it has been established that your pet has atopic dermatitis, the most logical solution would seem to be to prevent him from coming into further contact with the causative allergens. However, this solution is usually not feasible in everyday life.
There are several options for treating a dog with atopic dermatitis:
- Desensitization (=hyposensitization)
- Itching and anti-inflammatory drugs
- Support of the skin barrier
- Antimicrobial treatment
Different forms of treatment are often used side by side: a tailor-made treatment, so to speak, is created for each animal with atopic dermatitis. The key is for you as the owner to learn to discover which stimuli your animal reacts badly to and which medications he responds well to. This is a process that owner and vet and/or dermatologist go through together. On average, it takes a year to find a stable treatment strategy.
This treatment (also known as hyposensitization or allergen-specific immunotherapy = ASIT) involves injections of a desensitizing fluid. This contains extracts of the allergens to which the dog is hypersensitive. These injections are given according to a certain schedule in which the period between injections (the interval) increases and the dosage slowly increases to a certain maximum. It may take some time before the results of this treatment become visible: 6 months on average.
After 8-9 months, the treatment is evaluated. In 60-70% of dogs with atopic dermatitis, it is then found that a clear improvement has been achieved with this treatment. If desensitization is successful, the injections should be continued for life.
Not all dogs become completely symptom-free with this treatment. Therefore, a combination is often made with other forms of treatment, often aimed at supporting the skin barrier and/or controlling microbial inflammation. Especially in the first months of desensitization, when modest improvement can be seen, drugs that inhibit skin itching and inflammation are also often used as a temporary adjunct.
Itching and anti-inflammatory drugs
Corticosteroids work quickly and are cheap, but can have unwanted side effects with prolonged use of higher doses, such as heavy drinking and urination, weight gain, depression and eventually serious illnesses such as diabetes or Cushing's disease. This problem can sometimes be avoided by applying the corticosteroids not in the form of injections or tablets but on the skin itself in the form of an ointment, cream or spray. In atopic animals with ear infections, an ear ointment based on corticosteroids is indispensable.
Ciclosporin works somewhat more slowly than corticosteroids, is relatively expensive, but has fewer side effects: apart from mild gastrointestinal discomfort, few side effects are seen. Ciclosporin should be given for at least 8 weeks; if no improvement is seen after 8 weeks, treatment should be stopped. If the ciclosporins have a positive effect, then a decision can be made to reduce the dosage to every other day and possibly to every two days in the future. Antihistamines (such as cetirizine) only work in a small proportion of atopic animals. If the animal responds well to them, they can be used for longer periods of time without objection.
These drugs are sometimes given as the main treatment for atopy, or temporarily in addition to desensitization. If given as the main treatment, they should be given for life. An attempt can be made, however, to reduce the treatment to a maintenance dose. Like desensitization, this treatment is often combined with treatments aimed at improving the skin barrier. This can often lower the maintenance dose needed to suppress symptoms.
Various agents can be used to support the skin barrier:
- Moisturizing shampoos and lotions
- Feed supplements with omega3/omega6 fatty acids
- Feeds with an increased content of omega3/omega6 fatty acids
- Spot-on with omega3/omega6 fatty acids
Treatment of microbial dermatitis
Microbial dermatitis, i.e., inflammation due to yeasts or bacteria, must always be controlled because it is a major factor in the vicious circle of skin problems an atopic animal can get into. Through microscopic examination of skin material, your vet can determine whether there is a bacterial or yeast infection or a combination of both. A superficial bacterial infection can usually be treated using a mild antibacterial shampoo. If the inflammation is more severe, antibiotics should be used. Here, it is important to give the antibiotics for a sufficiently long time, i.e., at least three weeks. In case of a severe inflammation with a lot of crusting, an antibacterial shampoo can additionally be used. A yeast infection is usually treated with a special shampoo. Only in very severe cases is this not enough and medication in tablet form (ketoconazole) should be given.
Both bacterial and yeast infections of the skin tend to recur repeatedly, especially if the allergy is not yet completely under control. To prevent this, it is advisable to keep washing the animal regularly with a special shampoo against bacteria or yeast. Atopy is well treatable, each animal with atopy needs an appropriate treatment plan.
Do you have any questions following the above information? If so, please contact us.