Hello Monteck lc i.e. Montelukast+ levoceterizine as these both drugs are antihistamine and very much effective and as an anti allergic . These drugs acting very well in your wife case , it means she is having allergy . Your main concern is when she takes tablets , so symptoms , when stops , symptoms ( cough recurs ) . In my opinion your wife is having asthmatic allergic bronchitis . Please note down that mite, dust , hay , fodder, mold, pests , pollen , sudden increase or decrease in temperature are predisposing factors of allergy . However these both drugs are having minor side effects like sedation , dry mouth , drug dependence ( very mild degree ) but these are not major side effects , so your wife can use this drug for another 2-3 months . After that take these tablets ( combination ) on alternate day and there after twice in a week and in this way your wife will get rid off cough. Hot coffee and steam inhalation also help in allergy cases. Hope this will help you.