The answer to 'toilet foul smell' is that a foul odor coming from your toilet can be caused by a variety of issues, ranging from a clogged drain to a buildup of bacteria. Common symptoms include a persistent, unpleasant smell that doesn't go away even after cleaning. Some solutions you can try at home include plunging the toilet, cleaning the bowl with a toilet brush and disinfectant, and checking the wax seal for any cracks or leaks.
However, if the smell persists or you suspect a more serious problem, it's best to call in a professional plumber. They can thoroughly inspect the toilet and plumbing system to identify the root cause and provide the appropriate repairs or replacement.