Development of allergic diseases
For years, specialists have been drawing attention to the significant development of allergic diseases worldwide. This trend also applies to Poland. According to studies conducted as part of ECAP, allergic diseases may affect 25-30% of the population. In addition, we are also aware that the trend is increasing [1,2]. Among allergic diseases, the most common were:
- allergic rhinitis (25-31%),
- asthma (7-10%),
- atopic dermatitis (4-7%),
- food allergy (4-9%),
- systemic allergic reactions to hymenopteran insect venom (1-7.5%),
- urticaria (5-8%) [3].
Allergy – what to do?
Suppose a patient comes to us with a confirmed allergy. What can modern medicine offer him? Nowadays, allergy is treated in a comprehensive manner, based on several extremely important principles:
- when starting allergy therapy, the first step is to eliminate the allergens responsible for the clinical symptoms from the environment of the affected person. However, this is not always possible, especially in the case of inhalant allergens (pollen, mites, animal allergens) [9],
- pharmacotherapy is a safe and effective treatment for symptom relief. However, its action is ongoing and resolves when use is discontinued,
- biological therapy is a modern, safe and effective form of therapy currently aimed at a small group of patients with the most severe symptoms. The effects of this treatment disappear when it is discontinued [4],
- immunotherapy, commonly known as desensitisation, stands out as the only causal treatment. Through long-term administration of the allergen (over a period of 3 to 5 years), we induce the development of tolerance to the allergen used. Most importantly, the effect persists for many years after the end of therapy [5].
How does immunotherapy work?
As we have already mentioned, with immunotherapy we succeed in creating tolerance in the body to an allergen. This is worth emphasising because desensitisation is specific, meaning that we achieve tolerance to the allergen we administer to the patient. The effects of immunotherapy can appear after just a few weeks of use. If we start immunotherapy before the start of the grass pollen season, for example, the patient should already feel the effects during the first pollen season.
In the case of desensitisation to certain allergens, more time is needed to achieve the first effects. House dust mites are an example of this. In desensitisation to this allergen, a reduction in symptoms can be seen after about the first year of vaccine use. The patient can therefore reduce symptomatic treatment and even, in the case of people with asthma, notice an improvement in lung respiratory parameters.
What needs to be emphasised, however, is that yes – the first effect of immunotherapy is clear, but it is not permanent. If the patient stops treatment at this point, the effect will no longer be there in the following years. Therefore, immunotherapy should be continued despite the reduction of symptoms for 3 to 5 years.
Furthermore, recent studies show that immunotherapy can also change the course of the disease, i.e. act in a preventive way. This means that it can, for example, stop the onset of asthma in a patient with allergic rhinitis [6].
How can we deliver immunotherapy?
Desensitisation is not an achievement of recent decades. Immunotherapy was first introduced into clinical practice over a century ago by Leonard Noon. Initially, it was used only in the form of a subcutaneous vaccine. Other forms of immunotherapy (sublingual) did not appear until the 1980s [7].
How can we administer allergen vaccines today? At present, according to the recommendations of international and national scientific societies (European Academy of Allergology and the Polish Society of Allergology), two methods of administration are used:
- injectable, subcutaneous (SCIT), which is a vaccine administered by injection,
- sublingual (SLIT), administered as drops or tablets.
Both forms are safe and have high efficacy. In the case of injection immunotherapy, the patient has to visit the doctor’s office for subsequent doses. In contrast, the advantage of sublingual immunotherapy is that it can be taken at home [8].
Who can receive immunotherapy?
In light of the benefits that desensitisation can bring to a person with allergies, one might think that every patient should be referred for immunotherapy. However, it is not that simple. Studies have indicated that desensitisation cannot be used in every case. When should we refer for it? If the patient has a confirmed IgE-mediated allergy and suffers from one of the diseases:
- allergic rhinitis, which may be accompanied by allergic conjunctivitis or asthma,
- asthma,
- allergy to hymenoptera venom,
- conditionally, atopic dermatitis may be included, but only in those individuals with AD accompanied by allergic rhinitis, both of which are aggravated by contact with dust [9].
According to a commonly accepted algorithm, a patient should be qualified for immunotherapy in several steps. The first and most important is to confirm the presence of the disease, i.e. make a diagnosis. When starting the qualification for immunotherapy, we must also identify the allergen that is responsible for the severity of the symptoms. In this case, we use the patient’s history and the results of skin tests or blood tests for IgE antibodies to this specific allergen [9].
The second step, according to the algorithm proposed by Professor M.L. Kowalski, should be the evaluation of tests proving the efficacy of immunotherapy with this allergen. In making this assessment, the allergologist takes into account the scientific studies confirming the effect of the vaccine to be used. The specialist must also be sure that the patient will want to cooperate with him. This is very important because immunotherapy lasts several years and requires a great deal of regularity.
The last step in the guidelines mentioned is to establish the relative and absolute contraindications to immunotherapy.
Contraindications to immunotherapy – relative and absolute
Each time we qualify a patient, we need to consider the contraindications to immunotherapy. We divide these into two groups: absolute and relative. Absolute contraindications include:
- pregnancy, but with the proviso that a pregnant patient can continue immunotherapy but cannot start it,
- uncontrolled asthma,
- active autoimmune diseases (systemic lupus erythematosus, Sjögren’s syndrome, granulomatous vasculitis with eosinophilia, dermatomyositis) [10],
- age under five years,
- AIDS,
- cancer,
- psychiatric illnesses and addictions that prevent communication with the patient and full control of their treatment,
- eosinophilic oesophagitis [11,12].
The list of relative contraindications is much longer. The doctor qualifying a particular patient for immunotherapy should take these into account and weigh them individually against the benefits and possible risks for the patient.
However, temporary contraindications to immunotherapy include:
- acute infections,
- loss of asthma control or exacerbation of asthma,
- damage to the oral mucosa or dental procedures in the case of immunotherapy administered sublingually [13].
Safety of immunotherapy
Immunotherapy is a safe method. Crucially, it should be administered by a specialist with extensive experience. The patient, in turn, should be informed about the principles of treatment, the purpose, but also the possible risks. The fact that desensitisation is safe does not mean that we should not expect complications. Vaccine side effects can be divided into local and systemic. Local ones will vary depending on the method of immunotherapy.
When administered subcutaneously, the most common complications include:
- swelling,
- erythema,
- pain at the injection site.
On the other hand, if the patient takes immunotherapy orally, they may experience:
- itching, burning, swelling of the sublingual area, tongue and/or throat,
- abdominal pain.
Local adverse reactions are quite common. In the case of injection immunotherapy, these are swelling at the site of vaccine administration. In the case of sublingual immunotherapy, these are oral symptoms, which can occur in most people during the first week of use [17]. Importantly, however, they are mild and usually do not require discontinuation of treatment [18].
More serious for patients are systemic reactions, but these occur much less frequently. According to studies conducted in Europe, they may affect approximately 1.5% of children and 2.1% of adults receiving immunotherapy. They are more common after subcutaneous administration of the vaccine [18]. These types of reactions occur quite rapidly in patients, usually up to 30 minutes after administration of the immunotherapy preparation. They can be manifested by:
- urticaria
- nasal oedema
- angioedema,
- bronchospasm,
- anaphylaxis.
In contrast, systemic symptoms following sublingual vaccine administration additionally include:
- vomiting,
- abdominal pain,
- nausea,
- diarrhoea [19].
