Use a comma to separate nonessential elements from a sentence. More specifically, when a sentence includes information that is not crucial to the message or intent of the sentence, enclose it in or separate it by commas.
Genital warts are a sexually transmitted infection (STI) caused by certain strains of the human papillomavirus (HPV). These skin growths can cause pain, discomfort, and itching. They are especially dangerous for women because some types of HPV can also cause cancer of the cervix and vulva.
St. John's wort interacts with many different prescription and OTC drugs. It often causes the liver to break down drugs quickly from the body, reducing their effects. This is especially true with drugs that the liver processes in the same way that it breaks down St. John's wort.