WIll my landlord or a plumber be able to tell if I used drano/liquid plumber to try to clear a clog?

My bathroom sink is draining a little slow and lately gunk has come floating up. My lease specifically states that I am not allowed to use Drano type products. My question is why not? Is it bad for the pipes. And If I use something and it doesn't work will a plumber be able to tell? Any other advice about what I could use to clear the drain maybe something homemade or more natural?