Hi Thanks for your query L-montus contains levocetrizine montelukast combination. As such thses drugs do not have fatal side effects. Only some degree of sedation may be there for levocetrizine component. Some liver function derangement has been reported due to montelukast in the literature though no definite proof is not obtained till now. But as you are allergic on withdrawal of these drugs may cause relapse of your allergic symptoms. In fact allergy cannot be cured by these drugs. All they do is to reduce the symptoms on allergen exposure. For allergy cure specific immunotherapy may be of some help and for that you have to consult an allergist. Another thing is important here that you should always keep yourself aloof of this allergen exposure. Thank you.