There are many over the counter drain cleaners that promise fast results and no damage to your sink. The problem with most bathroom sinks is not because of clogs created by material that these chemicals are designed to stop but actually bits and pieces of items that fall into the bathroom sink. Items such as toothpaste caps or hair bows. Once these items get into the bathroom sink you’ll likely need a plumber to repair the problem. Using chemicals on this sort of problem can cause damage because you may not be able to remove the clog and the chemicals will remain in the bathroom sink too long which can be corrosive. Be sure to read all the warning labels on the chemicals before you use them and follow the instructions if you do decide to use chemicals on your drain. However, it’s best to get bathroom sink plumbing repair from a certified plumber.