If your site is blacklisted because of suspicious code or malwares, you will lose visitors from search traffic. It is very important to have a clean and healthy site. You can check if your site is blacklisted by different malware scanners by using VirusTotal.
You can scan a file or a web page by enter it’s URL. If your site used to be infected by malwares and you have fixed the issue, you should contact malware scanners to request a review.