For allergy problem if i take montelukast will it create any problem as i am trying to conceive?

Not likely: Montelukast is a category b medication when it comes to pregnancy and breast feeding suggesting that there is no known harm to humans. I am not aware of a study specifically evaluating impact on conception.

No: Medicines are rated in 5 pregnancy categories: a, b, c, d, and x. We try to avoid d's and x's in pregnant women. A's have demonstrated benefit for mom and fetus. C's usually have good safety data in animals and no identified problems in humans. B's have good safety data in humans. We can never say with 100% certainty, but a category b medicine such as monteleukast is considered safe.