Is it okay to take Allegra and Singulair at the same time ??

I do! And have for over 5 years. I don't have any issues with the combination

There are apparently no reactions between them. There is an interaction checker in the dark blue at the top of this page, for future help for you.

Yes, Allegra is an antihistamine and Singulair is a leukotriene receptor antagonist so they are two different types of drug.