Desensitization to grasses. When to start to avoid symptoms during the pollen season?

The main allergens responsible for seasonal allergy symptoms are grass pollen, which circulates in the air from late spring through summer until early autumn. The air above flowering meadows is thick with pollen, especially in May, June and the first half of July. Each plant produces up to a million grains, and there are around 9,000 species of pollinating grasses [1,2]. According to a study published nearly 20 years ago by ECAP, approximately one in five Poles is allergic to them [3].

Today, in an era of increasing incidence of atopic diseases, the prevalence of this type of allergy is probably even higher. In addition, the symptoms are becoming more and more troublesome. This is related to weather anomalies (pollen concentration increases with rising temperatures and sunlight) [4,5].

So how should grass allergies be treated? New-generation antihistamines and topical nasal corticosteroids are highly effective in treating hay fever (with itching and sneezing) [6]. If they are well chosen and used in the right dose, they bring quick and significant relief (reducing symptoms by over 70 to nearly 100%) [15]. However, these are temporary medications and do not provide long-lasting effects. Another solution, which is the only one that does not treat the symptoms themselves but targets the cause of the disease, is allergen immunotherapy, commonly known as desensitisation. This therapy significantly and permanently improves well-being while reducing the use of allergy tablets or nasal drops.

Desensitisation to grasses involves regular administration of allergen extracts in increasing doses. These are natural extracts available in the form of subcutaneous vaccines (injections) and sublingual vaccines (drops or soluble tablets). The high safety profile of sublingual vaccines allows them to be administered independently at home (daily or every other day) [1,12]. Traditional injection immunotherapy, on the other hand, requires regular visits to an allergist’s office (every 4–6 weeks) [8].

Immunotherapy can be used in both adults and children over 5 years of age [1,8,10]. To start desensitisation to grasses, you must be qualified for treatment by a specialist [10,12]. The decision should be preceded by thorough diagnostics, as the effect of the treatment largely depends on it.

In this case, molecular blood tests are the most effective, as they allow us to identify the allergenic molecules that cause our allergies. What does this mean? Grass pollen allergens (and others) consist of many different proteins with allergenic potential. For an allergen vaccine to work, it must contain the specific molecules that are responsible for the symptoms in a given patient [13].

When it comes to grasses, immunotherapy has been proven to be most effective for the proteins Phl p 1 and Phl p 5, which are the main allergens in timothy grass. Therefore, desensitisation is particularly recommended for people who are allergic to these two proteins [13].

However, it should be remembered that not every specialist deals with desensitisation. According to estimates, 40% of allergists do not perform immunotherapy [9].

Desensitisation to grasses – regardless of the allergen vaccine chosen and the administration schedule – begins at least several weeks before the pollen season, during the symptom-free period of the disease [10,11]. This should be 2–4 months before the start of the season, which falls at the turn of April and May. Therefore, February–March is the last chance to start desensitisation to grasses [11]. The aim is to reach the maximum dose of the vaccine before grass pollen appears in the air [12]. Immunotherapy is usually continued during the pollen season (with an appropriate reduction in dose) [1,10,12].

The results of studies conducted to date indicate significant and long-lasting benefits of immunotherapy [6]. In people allergic to grass pollen, this method offers a chance of up to 90% recovery [14]. Improvement is observed in both nasal symptoms (runny nose, itching) and eye symptoms (watering, itching, burning, redness) [1]. In addition, immunotherapy alleviates the natural course of the disease – it prevents the development of allergic asthma and further sensitisation [10].

How long do the effects last?

Desensitisation to grasses significantly reduces the severity of symptoms already in the first pollen season after the start of treatment [1]. Importantly, studies have been published showing that the reduction in symptoms persists for up to 12 years after the end of therapy [16]. However, the effectiveness of desensitisation can only be assessed after the entire treatment, which lasts 3–5 years. Completing the full cycle is a requirement for long-term effectiveness [7].

During desensitisation to plant pollen, serious side effects (anaphylaxis, angioedema, exacerbation of asthma) occur sporadically, especially in the case of safer sublingual immunotherapy [7,8]. However, mild to moderate side effects, such as itching of the mouth, throat irritation, and swelling of the mouth, occur in over 80% of patients. These symptoms usually resolve spontaneously and are generally not a reason to discontinue immunotherapy [1].

Aleksandra Lipiec 

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translation: Julia Majsiak