Herpes simplex type 1 is a herpes virus that causes cold sores and fever blisters in and around the mouth. In rare cases, when someone's immune system is severely compromised, this virus can cause infection of the brain (encephalitis), requiring intravenous therapy. Herpes simplex type 1 is also known as herpes simplex virus type 1 (HSV-1) human herpesvirus 1 (HHV-1). QUESTION Ringworm is caused by a fungus. See Answer From Skin Problems and Treatments Resources Skin Care for PsoriasisIs Your Skin Trouble Blocked Hair Follicles?How Psoriasis Affected An Actress' Career Featured Centers Good and Bad Foods for PsoriasisVideo: Getting Personal on Life With MS Health Solutions From Our Sponsors Shot-Free MS Treatment Your Child and COVID-19 References Jameson, J. Larry, et al. Harrison's Principles of Internal Medicine, 20th Ed. New York: McGraw-Hill Education, 2018.