Learn how certain drug interactions or an increase in the dose of certain drugs can cause serotonin levels to rise to potentially dangerous levels.
Disease
Severe acute respiratory syndrome (SARS)
Learn about this contagious and sometimes fatal respiratory illness. The last known infection was reported in 2004.
Disease
Sex headaches
Learn about the causes and treatment of this type of headache.
Disease
Sexually transmitted diseases (STDs)
Find out the symptoms of STDs and what you can do to prevent them, along with the treatments if you're diagnosed with one.
Disease
Sezary syndrome
Find out more about the symptoms, diagnosis and treatment of this rare type of cancer.
Disease
Shaken baby syndrome
Understand why shaking a baby can cause brain damage, and why getting immediate medical care can save a child's life or prevent serious health problems.
Disease
Shellfish allergy
It's possible to be allergic to some types of shellfish without reacting to other types. Learn more about this common food allergy.
Disease
Shigella infection
This infection of the intestine causes diarrhea. Learn the symptoms, treatments and ways to help prevent it.
Disease
Shin splints
This pain along the shin bone is common in runners, dancers and military trainees. Learn how to prevent shin splints.
Disease
Shingles
Learn more about symptoms, causes, treatment and vaccine prevention of this painful condition affecting the nerves.
Disease
Short bowel syndrome
Learn about how the body may not get enough nutrients when the small intestine is short because of surgery or a condition present at birth.
Disease
Sick sinus syndrome
This heart rhythm disorder causes slow, paused or irregular heartbeats. Learn the symptoms and how it's treated.