Hello Paul, Thank you for asking at HCM. Yes, Montek LC is effective for allergy & asthmatic problem. It is effective both for allergic rhinitis & asthma. It s good that you can manage your allergies by using it on SOS basis. Well, using it on SOS basis is good approach for allergic rhinitis (nasal symptoms). But unless your asthma is of very mild severity (intermittent symptoms only), I would suggest to use it regularly. If you have seasonal allergies, you can start Montek LC 2 weeks before expected bad season and continue daily during the season. Regarding your question of stopping asthma & allergy, I would say, Montek LC does not cure allergies. But allergy & asthma are, by themselves, dynamic in nature, they come & go, they change their severity over period of time. So as long as you are having them, I would suggest you to take the drug. So unfortunately doctors cannot predict how long one needs to take allergy medications. Basic ingredient drugs in both Montek LC & Montair LC are same - montelukast & levocetirizine. Most common side effect is sedation due to levocetirizine. Occasionally some patients may report headache, impaired concentration, nausea, very rarely depressive thoughts. But if you don t have any of these side effects, it is safe for long term use. Hope this will be helpful to you. Wish you best of the health. Regards.