What is allergen immunotherapy? Allergen immunotherapy, as the term suggests, can help alleviate irritating allergies and cross-allergies and also prevent future ones – we will explain how this works and which allergies can be treated in our article.
In the United Kingdom, around 33 per cent of adults suffer from at least one allergy. Especially when allergic reactions are triggered by unavoidable elements like house dust, pollen or food, allergies can severely interfere with everyday life. Allergen immunotherapy is the only approved treatment that can provide lasting relief: it causes sufferers to tolerate the triggers of the allergy better.
Read up on how allergen immunotherapy works – that is, how allergy injections and hayfever injections are given – which allergies can be treated, and tips you can use to alleviate side effects during treatment.
What is allergen immunotherapy?
Allergen immunotherapy, also called specific immunotherapy, desensitisation treatment or hyposensitisation, is currently the only way to permanently treat some respiratory allergies and allergies to wasp or bee venom.
The name hyposensitisation gives you clue as to the aim of the treatment: ‘hypo’ comes from the Greek and means ‘under or beneath’. Hyposensitisation aims to make your body react less sensitively to normally harmless substances that trigger your allergy. This works by acclimatising the body to the allergen over a longer period of time. If this is successful, the body becomes more tolerant to the allergen.
But good things take time: successful treatment occurs through continuous, regular treatment with allergen injections over a period of at least three years. Exactly how the body’s immune system is changed through allergen immunotherapy has not yet been researched in detail.
Why treat an allergy?
What happens when you have an allergy? With an allergy, the immune system reacts strongly to a substance that is actually harmless, the allergen. With a pollen allergy, for example, allergens include certain tree, grass pollens or specific pollen, such as birch pollen.
Some people’s immune system reacts excessively sensitively when it encounters an allergen – and triggers an inflammatory allergic reaction. Symptoms include a sniffling nose, coughing and sneezing or swollen eyes, but also skin reactions and digestive problems. In the long run, 40 per cent of hayfever cases that are not treated carefully can even develop into allergic asthma.[2, 3]
Curious to find out how other allergens affect the body? You can read more about food allergies in our dedicated article on food allergies and intolerances.
Does allergen immunotherapy work?
Allergy injections or tablets can currently only be administered against a few allergies. There are approved therapeutic allergens for treating these specific allergies:
- Grass, cereal and herb pollen allergy
- Tree pollen such as birch pollen allergy
- House dust allergy
- Wasp and bee venom allergy
In some cases, allergen immunotherapy treatment can also be carried out with non-approved therapeutic allergens. This is possible, for example, when it comes to a pet allergy or mould allergy. However, it may be that the composition of therapy allergens used is not effective enough. So, make sure you talk to your doctor about suitable treatment options.[4, 6]
Can you have allergy shots for food allergies?
Other allergy triggers are currently being researched for treatment through allergy injections. For example, food allergies such as a nut allergy, which require special treatment due to their severity, have only recently been treated successfully in studies. Using allergen immunotherapy for food allergies such as milk allergy and egg allergy is still being researched extensively.
However, there are still some problems with the treatment. Severe side effects often occur. In addition, it has not yet been conclusively researched how long you remain tolerant to the allergen. That is why allergy injections for food allergies has so far only been used in studies.[7–9] It is important to note that researchers are currently looking to allergy injections to treat food allergies, rather than to cure them.
Allergen immunotherapy: how does allergy diagnosis work?
Before starting treatment, you must first determine the exact allergy trigger. You can do this with your doctor or with a home allergy tests, which will identify exactly which allergen your immune system reacts to. After all, how successful allergy injections and medication are depends, above all, on whether they contain the right allergen extract. To determine the exact allergen, not only skin tests are usually used but also blood tests during which, for example, specific IgE antibodies are examined in your blood.[10, 11]
Did you know that researchers have found that allergy triggers often contain not only one allergen, but also major and minor allergens. If you are allergic to a major allergen, hyposensitisation is most effective, but if you are allergic to minor allergens, it may be less effective.
If you know the allergen triggering your reactions, doctors can choose which allergen preparation to use. Allergy sufferers are then given the drug repeatedly over a long period of time, with the dose steadily increasing. There are multiple ways of carrying out allergen immunotherapy, with different durations and approaches.
How long does allergen immunotherapy take?
The more traditional approach to allergen immunotherapy consists of a phase during which the dosage increased and a maintenance phase. First, the allergen is injected on a weekly basis during the first phase, with the dose increasing every week. This period usually lasts 16 weeks.
After you have reached the highest dose, you will be injected with the maintenance dose, with which you will be injected once a month for three years. If you are treating a pollen allergy, such as pollen allergy, then the allergen concentration can be adjusted or suspended during the pollen season.
There are also other approaches to hyposensitisation, including one where the phase of increasing the dosage is shorter, and the maintenance phase is longer. Overall, this method takes the same amount of time as the method described above.
What is cluster immunotherapy (rapid desensitisation)?
During cluster immunotherapy, the phase during which the dosage is increased is carried out particularly quickly. During an inpatient stay in a clinic, you will be administered several injections daily so that you become tolerant as quickly as possible.
Subsequently, the maintenance dose is administered monthly for at least three years. This procedure is often used for insect venom allergies, from which people affected suffer more severe allergic reactions such as anaphylactic shock. Therefore, it is important that insect venom allergy sufferers build up a higher tolerance to the allergen more quickly.
Subcutaneous vs sublingual immunotherapy: what’s the difference?
The active allergen can be administered in two ways – subcutaneously and sublingually:[3, 4]
- Subcutaneous immunotherapy (SCIT) is when you receive an injection from your doctor into the subcutaneous fatty tissue of your upper arm.
- Sublingual immunotherapy (SLIT) is when you place drops or tablets under your tongue.
You can carry out sublingual immunotherapy yourself at home. This involves putting a tablet or liquid under your tongue every day for a period of three years. However, this treatment has only been adequately researched for a few allergies, such as grass pollen allergy. It is recommended if subcutaneous treatment is not an option for you – for example, because of other diseases or circumstances.
Is allergen immunotherapy worth it?
Allergen immunotherapy is complex and takes a long time. Nevertheless, it is a promising form of treatment: treatment is successful for two-thirds of those that opt for it. After one year, many of those affected already notice an improvement when it comes to sneezing, itching eyes or watery eyes. However, the full effect only can only be felt two to three years after treatment. In addition, younger people, in particular, benefit from allergy injections and tablets, as they can protect against allergic asthma or other allergies.[10, 12]
Another advantage is that hyposensitisation can prevent troublesome cross-allergies. If you are able to tolerate a pollen allergy better, seasonal reactions to allergens with a similar protein structure, such as stone fruit if you suffer from birch pollen allergy, may also improve.
Tips during treatment: what do you do for an allergy shot?
By following these tips, you can maximise the efficacy of your allergen immunotherapy treatment:[3, 5]
- Avoid moderate physical exertion or heat (such as going to the sauna) on the day of treatment or when you start your treatment with tablets or drops.
- Take anti-allergic medication if you have symptoms, as this will not affect the success of the treatment and will help you to keep symptoms at bay.
- Talk to your doctor regularly about allergic reactions, even if they are caused by other triggers and about illnesses, vaccinations or medications you are taking (especially beta blockers).
- Do not take allergens in the form of drops or tablets immediately after or before brushing your teeth and wash your hands after taking them, so that you do not get the allergen in your eyes or nose.
- Keep regular appointments with your doctor and follow instructions you are given for sublingual hyposensitisation.
Are there any side effects from allergy injections or tablets?
Hyposensitisation is usually well tolerated, as preparations have been used for over a hundred years and are well researched.[4, 13] Nevertheless, many precautions are usually taken to make treatment as harmless and pleasant as possible. For example, sufferers are screened with allergy diagnostics before starting treatment and are observed after each dose.
Especially during the first weeks of increasing the dosage, allergic reactions, tiredness or headaches may occur, as the body is not yet used to the allergen. If you are given injections, you may experience itching and swelling at the site of injection.
When administered sublingually, 40 to 75 per cent of those treated experience temporary reactions in the form of itching, irritation or swelling in the mouth, especially during the first weeks of treatment.[3, 4] With people being treated for allergic asthma, lung function is examined 30 minutes after an injection.
If the side effects are severe, the dose of the allergen is reduced for future treatments. If doctors find a cause for the severe side effects and can eliminate it, they can also increase the dose again.
Can immunotherapy cause anaphylaxis?
An anaphylactic shock is the most severe allergic reaction that can affect the whole body and requires rapid medical attention. Rashes, severe itching, stomach pain or cardiovascular problems may occur. In the worst case, an anaphylactic shock can lead to cardiovascular or respiratory arrest and can therefore be fatal.
But anaphylaxis during hyposensitisation is very rare among otherwise healthy people. According to studies, a severe allergic reaction occurred after less than one in 10,000 injections, most often breathing difficulties. An anaphylactic shock after allergy injections or tablets is thus considered rare.
Although severe allergic reactions are very rare after hyposensitisation, your doctor will still ask you to stay in the surgery for 30 minutes after each of your treatments, so that they can observe you and intervene quickly in the unlikely event of a severe reaction. In an emergency, your doctor can help you quickly with anti-allergic drugs, cortisone or epinephrine.
Risk factors that can lead to more complicated side effects or anaphylactic reactions include:
- Certain heart problems or cardiovascular disease
- Taking beta-blockers
Tell your doctor if any of these risk factors apply to you, or if you have already had an allergic reaction to allergen immunotherapy.
What is allergen immunotherapy – at a glance
What is allergen immunotherapy?
Allergen immunotherapy is the only treatment that can make the body less sensitive to an allergen. This is especially important for allergies to triggers that are difficult for sufferers to avoid – for example, pollen or house dust allergies. However, there is currently no proven treatment for food allergies.
How does hyposensitisation work?
Hyposensitisation accustoms the body to ever-increasing amounts of the allergen by means of allergy injections or hayfever injections into the upper arm or tablets or drops placed under the tongue. Treatment lasts at least three years and always consists of two phases.
In the phase during which dosage is increased, the active substance that triggers the allergy is administered either weekly, daily or hourly in increasingly higher doses, depending on the exact form of treatment. In the subsequent maintenance phase, the maximum dose of the active substance achieved is administered monthly over a long period of time until treatment has spanned a total of three years.
What are the possible side effects?
Allergic reactions from allergy injections or medication such as redness and swelling may occur. If you take the active substance by mouth you may especially experience itching, burning and swelling in some cases. More severe allergic reactions are very rare. Less than one in 10,000 syringes causes a severe allergic reaction.
What do I need to know before allergen immunotherapy?
Stay in the doctor’s office for 30 minutes after receiving allergy injections or hayfever injections, avoid heat and strenuous exercise immediately before and after treatment, and discuss medication, allergic reactions and medical conditions with your doctor to reduce the risk of a severe reaction and to get immediate help if you have a severe reaction.
If you take the medicine orally, do not take it immediately before or after brushing your teeth. Wash your hands thoroughly after taking the medicine, so that you do not accidentally irritate your eyes or nose with the medicine.
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