This medical emergency involves sudden loss of all heart activity. Learn how fast, appropriate care may help prevent death.
Disease
Sudden infant death syndrome (SIDS)
Learn about the unexplained death of a young baby who seems healthy.
Disease
Suicide and suicidal thoughts
Suicide can be prevented. Learn suicide warning signs and how to reach out for immediate help and professional treatment.
Disease
Sun allergy
Learn more about the causes, symptoms and treatment of this itchy rash that is an allergic reaction to sunlight.
Disease
Sunburn
Learn more about how UV rays harm your skin and what you can do for symptom sunburn relief and how to protect yourself from sun exposure.
Disease
Supraventricular tachycardia
SVT is a heart rhythm disorder that causes a very fast or erratic heartbeat. The heart may beat more than 150 times a minute. Know the symptoms and when it's treated.
Disease
Suspicious breast lumps
Most of these growths aren't cancer, but you should still get them checked promptly.
Disease
Sweating and body odor
Learn more about the causes, treatment and self-care of these natural and common skin conditions. Unusual changes may mean a health problem.
Disease
Swimmer's ear
The moisture from water left in the ear after swimming or bathing can lead to this infection in the outer ear canal.
Disease
Swimmer's itch
Learn more about the symptoms, treatment and prevention of this itchy rash that usually affects people swimming in freshwater lakes.
Disease
Swollen knee
This condition can be caused by trauma, overuse injuries, or an underlying disease or condition. A fluid sample from the knee may be needed for diagnosis.
Disease
Swollen lymph nodes
Infection from bacteria or viruses most often causes this condition.