ASIT naïve patients sensitized to grass pollens will be recruited for the study. All of them will be instructed to treat bothersome in-season symptoms when they appear (on as needed, pro re nata basis) with rescue medication. They will be given 5 different options and will be informed about the effects of each of them in order to make their optimal choice for different symptoms and their combination: local decongestant (xylomethazoline, when congestion is leading), local antihistamine (azelastine, when itching, sneezing and rhinorhea a predominant), nasal corticosteroid (momethasone, when all nasal symptoms are pressing and no adequate relief is obtained form the other 2 local treatments), oral antihistamine (bilastine, when itching and sneezing persist despite the local treatments) and oral corticosteroid (prednisolone, when any or all symptoms become unbearable despite the other suggested treatments). Patients who are reluctant to use immunotherapy or who are too late to initiate it will be randomized to be treated with the listed medications on as needed basis, the nasally applied formulations will be followed by either HPMC to prolong and enhance their effect (Group HPMC) or placebo (lactose powder) (Group Placebo) to serve as control. Patients indicated and willing to carry out ASIT will be treated according to the standard protocol with grass allergens sublingually (Staloral #688) and will receive rescue medication (Group Immunotherapy).

Rationale. Assessment and follow up of specifically sensitized subjects with allergic rhinitis during the pollen season is traditionally based on symptom scores. Accounting for the use of rescue medication on top of symptom scores provides another dimension to the overall clinical characterization of the patients. Thus, using "combined symptom and medication scores" (CSMS) allows thorough characterization of the disease course. Guidelines recommend that CSMS are used for assessment of the effect of allergen specific immunotherapy in subjects with allergic rhinitis. Different allergic rhinitis management strategies can be evaluated and compared by means of CSMS. In the update of the ARIA guidelines of 2010, 24 recommendations have been made in relation to pharmacologic treatment. Special position paper has been devoted to severe chronic upper airway disease (SCUAD), the treatment for which has been earmarked as unmet need.

Consequently, a standardized and universally recognized rescue treatment strategy does not exist. The most common approach for handling nasal complaints in real life consists in using rescue medication for symptoms whenever they appear. This is certainly the case when symptoms appear for the first time ever, or when patients do not want to resort to allergen specific immunotherapy (ASIT) and / or regular oral antihistamine treatment for financial reasons or personal beliefs. Under these circumstances, a long list of pharmacological choices for local or systemic application is possible including antihistamines, corticosteroids, leukotriene antagonists, cromones and antimuscarinic drugs.

Formulations for local application in the nose appeal to patients with their ease of use and immediate relief. They comprise a variety of generic drugs: decongestants, antihistamines, corticosteroids and antimuscarinics. The fact that they are not ingested makes them first choice for people reluctant to take oral medications. In many cases it is possible to control the symptoms of allergic rhinitis with these formulations used per se or as adjunct rescue medication in the course of ASIT.

The question stays whether the effectiveness of nasally applied drugs can further be improved. Despite the good rationale for their mechanism of action, their efficacy is diminished by the cleaning mechanisms of the nose, rhinorrhea in particular. Slowing down of the clearance of the nasal mucosa and prolonging the contact time with the nasal mucosa would enhance their pharmaceutical effects. The investigators have demonstrated by objectively measuring nasal flow rates that "sealing" in place locally applied oxymetazoline in subjects with persistent allergic rhinitis by means of commercially available hydroxyl-propyl-methyl-cellulose (HPMC) significantly enhances the resulting decongestion and that this effect is augmented over a time span of 2 weeks without noticeable tachyphylaxis or adverse events.

The investigators set the aim to investigate whether this beneficial effect of HPMC translates into clinical benefits in a real life clinical trial for other available drug preparations for nasal delivery.

Study design. ASIT naïve patients sensitized to grass pollens will be recruited for the study. All of the patients will be instructed to treat bothersome in-season symptoms when they appear (on as needed, pro re nata basis) with rescue medication. The patients will be given 5 different options and will be informed about the effects of each of them in order to make their optimal choice for different symptoms and their combination: local decongestant (xylomethazoline, when congestion is leading), local antihistamine (azelastine, when itching, sneezing and rhinorhea a predominant), nasal corticosteroid (momethasone, when all nasal symptoms are pressing and no adequate relief is obtained form the other 2 local treatments), oral antihistamine (bilastine, when itching and sneezing persist despite the local treatments) and oral corticosteroid (prednisolone, when any or all symptoms become unbearable despite the other suggested treatments). Patients who are reluctant to use immunotherapy or who are too late to initiate it will be randomized to be treated with the listed medications on as needed basis, the nasally applied formulations will be followed by either HPMC to prolong and enhance their effect (Group HPMC) or placebo (lactose powder) (Group Placebo) to serve as control. Patients indicated and willing to carry out ASIT will be treated according to the standard protocol with grass allergens sublingually (Staloral #688) and will receive rescue medication (Group Immunotherapy).

Inclusion Criteria:

• Male or female patients
• Age ≥ 18 and ≤ 55 years
• Personal history of rhinitis during the pollen season
• Moderately severe / severe seasonal allergic rhinitis (grass)
• Positive skin prick test for grass/cereals

Exclusion Criteria:

• Subjects with arterial hypertension, arrhythmia or evidence of heart ischemia
• Subjects with other serious chronic comorbidities and bad therapeutic control
• Subjects with nasal polyposis
• Any contraindications for xylometazoline
• Any contraindications for HPMC
• Any contraindications for azelastine
• Any contraindications for bilastine
• Any contraindications for mometasone
• Any contraindications for prednisolone
• Subjects unable to give informed consent
• Pregnant or lactating women