Allergic disease

RAGWEED ALLERGY DIAGNOSIS AND TREATMENT

RAGWEED ALLERGY DIAGNOSIS

Diagnosis of ragweed-induced allergic rhinoconjunctivitis and asthma relies on patient’s precise medical history, especially regarding potential sources of exposure, seasonal symptoms of nasal inflammation and airway hyperresponsiveness.

Symptoms of ragweed-induced allergic rhinoconjunctivitis include sneezing, nasal itching and obstruction, watery nasal discharge, eye itching and congestion, and tearing, while coughing episodes, difficulty breathing or wheezing are associated with asthma; all these symptoms correlate with and may last beyond the pollen season.

The main clinical test used in practice is the skin prick test, which can be accompanied by investigations such as nasal challenge and spirometry. Paraclinical testing allows the identification of sensitizing allergens and cross-reactions by measuring specific serum IgE to relevant allergens.

RAGWEED ALLERGY TREATMENT

THE COMPLEX THERAPEUTIC APPROACH MUST INCLUDE:

Ragweed pollen avoidance

Ragweed pollen avoidance can improve allergic rhinoconjunctivitis symptoms. Exposure to pollen can be decreased by using air conditioners to filter the air, by keeping windows closed during daytime, and by decreasing the time spent outdoors during the peak of the pollen season. An important challenge in Europe nowadays is limiting ragweed spread, which can be done by different methods, such as herbicides, mowing, or weeding. However, this approach is difficult to achieve in the regions with high pollen counts.

Symptomatic treatment

Symptomatic treatment of ragweed-induced rhinoconjunctivitis includes several agents found in systemic and topical dosage forms, out of which the traditional mainstay are second-generation (non-sedating) H1-antihistamines and topical corticosteroids. For ragweed-induced allergic asthma, the main therapeutic classes are inhaled corticosteroids (ICS) and beta2-agonists. However, symptomatic treatment only ensures good disease control in less than 50% of patients and has side-effects such as drowsiness, dizziness, dry mouth (antihistamines), and nasal mucosa dryness, burning sensation and epistaxis (glucocorticoids). Proposals for new symptomatic treatments, nearing clinical application, include selective histamine-H3 receptor antagonists, leukotriene B4 receptor antagonists, and selective DP2 receptor antagonists.

Allergen-specific immunotherapy (SIT)

Allergen-specific immunotherapy (SIT) is the only disease-modifying treatment for allergies. It interferes with the pathological immunologic mechanisms that lead to the development of allergy. SIT significantly alleviates allergic symptoms, thereby decreasing the need for symptomatic medication, and it also offers long-term protection and prevents the development of asthma in people who already have allergic rhinoconjunctivitis. The main route of administration has been subcutaneous (SCIT), but recently sublingual immunotherapy (SLIT) has been gaining considerable interest. It is recommended to administer SIT for at least 3 to 5 years, in order to induce a strong immune response against allergens and to ensure long-term protection. Recent studies revealed that compliance to SCIT is significantly higher than for SLIT (Egert-Schmidt et al, 2014).

SCIT involves the administration of a course of injections, starting with a very low dose of allergen and building up gradually until a plateau or maintenance dose is achieved. Maintenance injections are then given at 4- to 6-week intervals for 3 to 5 years.
SLIT involves daily sublingual administration of allergen drops or tablets (available since 2014), for a period of 3 to 5 years.

Currently, most SIT products are still prepared from poorly defined allergen extracts (Valenta et al, 2012). However, as more allergen molecules are being structurally characterized, it has become possible to produce well-defined recombinant and synthetic molecules, coupled allergens, and genetic vaccines. Other SIT improvements include the addition of omalizumab or adjuvants (with toll-like receptor agonist activity), cell-based approaches (allergen-expressing stem cells, engineered T regulatory cells, engineered Th1 cells), the use of different administration routes (intralymphatic, epicutaneous), and passive immunization with allergen-specific antibodies. So far, SIT has not been developed as prophylactic vaccination with the aim of preventing allergic sensitization. This challenging new approach is still in early research phases, and it could represent a significant advancement (Fig. 1). The prophylactic treatment would obviously be a major step forward because it would not be limited to the treatment of allergic patients, but would also prevent allergies and, hence, stop the currently exploding allergy epidemic.