Hello dear, The presence of increased levels of IgE antibody indicates that your child is sensitized to certain allergens. And the immune system of the body reacts on coming in contact with such allergens. Montelukast preparations- used as a maintenance therapy to relieve symptoms of seasonal allergies & asthma. Romilast L also contain Cetrizine, an anti histamine preparation which provides symptomatic relief. The decision about how long to continue the drug should be taken by the treating physician based on the clinical findings & co-relating them with the investigation reports. Till then, make sure your child maintains adequate hydration, proper nutrition & is well protected from dust, cold & other allergens. You can ask me any further queries using the below link: http://www.healthcaremagic.com/doctors/dr-polash-sannigrahi/64925 Wishing him a Good Health. Thanks & take care.