In-depth

Addison's disease

Addison's disease occurs when your adrenal glands produce insufficient amounts of certain important hormones. Treatment may include taking corticosteroids.

Agoraphobia

Do you feel trapped in your own home? Do you worry about having a panic attack? Find out how agoraphobia can be treated.

Amyloidosis

Anaphylaxis

Anaphylaxis is the most serious type of allergic reaction. It often occurs rapidly after exposure to an allergen and may be life-threatening.

Anthrax

Antibiotic-associated diarrhea

Antibiotics save lives, but they can also have side effects. The most common are mild to severe diarrhea and a serious type of colitis.

Appendicitis

Ascariasis

Bee stings

Bee stings — Comprehensive overview covers prevention, treatment of bee stings.

Behcet's disease

Behcet's disease affects several body systems and causes a variety of signs and symptoms. Find out what it is and how it's treated.

Bird flu (avian influenza)

Blastocystis hominis infection

A microscopic parasite causes Blastocystis hominis infection. Experts disagree as to whether this infection causes diarrhea and other associated signs and symptoms.

Blind loop syndrome

C. difficile

C. difficile can be a life-threatening infection. It typically develops when antibiotics destroy other bacteria in your intestines, allowing C. difficile to flourish.

Carcinoid syndrome

Carcinoid tumors

Carcinoid tumors are rare, slow-growing cancerous tumors that most often occur in the gastrointestinal tract or in the lungs.

Celiac disease

Celiac disease is an immune reaction to gluten, a protein found in certain foods. As a result, the body is unable to absorb some important nutrients.

Chagas disease

Cholera

Cholera causes severe diarrhea and can kill in a matter of hours, yet can be easily treated with oral or intravenous fluids.

Churg-Strauss syndrome

Churg-Strauss syndrome is a rare disorder marked by blood vessel inflammation that affects organs throughout the body. Asthma is the most common sign.

Colon cancer

Colon cancer and rectal cancer combined are the second-leading cause of cancer-related deaths in the United States. Regular screening tests can help reduce your risk.

Colon polyps

Crohn's disease

Cryptosporidium infection

Cryptosporidium infection may cause diarrhea in healthy people, but for people with HIV/AIDS and weakened immune systems, the illness can cause serious complications.

Cyclic vomiting syndrome

Cyclic vomiting syndrome can last for hours or days and shares many triggers with migraines.

Cyclospora infection

Cytomegalovirus (CMV) infection

Diabetes insipidus

Diabetes insipidus is a rare condition characterized by intense thirst and the excretion of large amounts of urine.

Diabetic neuropathy

Diverticulitis

Drug allergy

E. coli

Ear infection (middle ear)

Ear infections are common in children. These bacterial or viral infections of the middle ear can cause mild to severe ear pain.

Ebola virus and Marburg virus

Ehrlichiosis

Ehrlichiosis is a tick-borne disease that causes flu-like symptoms. When you're outdoors, be aware of steps to prevent tick bites.

Endometriosis

Endometriosis is a common and often painful disorder in which tissue that normally lines the inside of your uterus grows outside your uterus.

Fecal incontinence

If you have difficulty controlling your bowel movements, don't shy away from talking to your doctor — effective treatments for fecal incontinence are available.

Food poisoning

Food poisoning has many forms, and some can be serious. Here's how to recognize food poisoning and ways to prevent getting sick.

Giardiasis

Giardia infection is a common waterborne illness. Learn the symptoms and reduce your risk.

Graves' disease

Hantavirus pulmonary syndrome

Hantavirus pulmonary syndrome is initiated by a rodent-carried virus that infects the lung tissues, bringing on flu-like symptoms, respiratory problems and even death.

Hirschsprung's disease

Hirschsprung's disease, a disease of the colon, is present at birth and can cause serious problems passing stool.

HIV/AIDS

More than 39 million people are living with HIV — the virus that causes AIDS. Millions more are likely to become infected in the next decade.

Hunter syndrome

Hunter syndrome, a rare metabolic disorder, occurs when the body can't break down certain complex sugars. Complications occur as these sugars accumulate in the body.

Inflammatory bowel disease (IBD)

Intestinal ischemia

Intestinal ischemia occurs when the blood supply to your digestive system is reduced. Abdominal pain is a common symptom. Several treatment options are available.

Intestinal obstruction

Intestinal obstruction — a serious condition that requires prompt medical attention — occurs when a blockage of the intestine prevents food or fluid from passing through.

Intussusception

A rare but serious disorder, intussusception occurs when one part of the intestine slides into an adjacent part, often causing intestinal obstruction.

Irritable bowel syndrome

Ischemic colitis

Ischemic colitis is a disorder in which the colon becomes inflamed, usually due to a disruption of blood flow.

Jet lag disorder

Flying across multiple time zones disrupts your natural body rhythms, leading to sleep problems and other symptoms. Learn how to put jet lag to rest.

Kawasaki disease

Kawasaki disease — the leading cause of acquired coronary disease in children — causes artery wall inflammation throughout the body. It affects children younger than age 5.

Lactose intolerance

Legionnaires' disease

Legionnaires' disease, a severe form of pneumonia, is caused by bacteria that can live in water in air conditioning systems, showers and spas.

Listeria infection

Most people exposed to listeria don't become ill. But for those at risk of a listeria infection — a foodborne illness — the consequences can be severe.

Malaria

Malaria is one of the oldest diseases on Earth and is still one of the leading killers.

Mesenteric lymphadenitis

Mesenteric lymphadenitis is an inflammation of the lymph nodes in the tissue that attaches various organs to your abdominal wall (mesentery). It mainly affects children.

Milk allergy

Myocarditis

Myocarditis is a disease in which the heart muscle becomes inflamed and swollen, often as the result of an infection.

Nicotine dependence

Breaking your addiction to nicotine is difficult and takes commitment, support and time. But doing so can make a huge difference in your overall health.

Norovirus infection

Noroviruses cause an intestinal flu-like illness that typically resolves within days. Norovirus infection is highly contagious, especially in closed settings like hospitals and cruise ships.

Ovarian hyperstimulation syndrome

Ovarian hyperstimulation syndrome (OHSS) — Comprehensive overview covers symptoms, treatment of this complication of infertility treatment.

Peanut allergy

Pelvic inflammatory disease (PID)

Peritonitis

Plague

Plague is a disease carried by rats and other rodents. The risk of developing plague is low, and most cases occur in Africa.

Porphyria

Porphyria is a group of inherited disorders that result from buildup of natural chemicals call porphyrins, which can cause nervous system and skin problems.

Premenstrual syndrome (PMS)

Preterm labor

Primary biliary cirrhosis

Primary sclerosing cholangitis

Proctitis

Pseudomembranous colitis

Pseudomembranous colitis is an inflammation of the colon that occurs most often in people using antibiotics.

Q fever

Radiation sickness

Radiation sickness is the effect of high doses of radiation on the body. The severity of illness depends on how much radiation the body absorbs.

Reye's syndrome

Roseola

Rotavirus

Rotavirus causes severe diarrhea in infants and children. Most cases can be treated at home with extra fluids.

Serotonin syndrome

Serotonin syndrome — caused by mixing some antidepressants and other medications — can be life-threatening if left untreated.

Severe acute respiratory syndrome (SARS)

Severe acute respiratory syndrome (SARS) has sickened people worldwide. Although effective treatments aren't yet available, common-sense precautions may help you avoid infection.

Shellfish allergy

Shigella infection

Shigella infection (shigellosis) is a disease that causes diarrhea. Young children are most likely to get the disease, but it can spread to anyone.

Smallpox

Social anxiety disorder

Swine flu (H1N1 flu)

Swine flu — Comprehensive overview covers swine flu symptoms, tests, treatment and prevention.

Tapeworm infection

Toxic shock syndrome

Trichinosis

Tularemia

Tularemia is a rare, highly infectious disease spread by insects and wild animals. Landscapers, hunters and laboratory workers are especially at risk.

Typhoid fever

Although rare in industrialized nations, typhoid fever is a serious threat in many parts of the world. Learn how to stay safe when you travel.

Ulcerative colitis

Vesicoureteral reflux

Vitamin deficiency anemia

Lacking certain vitamins can lead to vitamin deficiency anemia. Find out which vitamins are linked to this condition.

Wheat allergy

Whipple's disease

Whipple's disease is a rare bacterial infection that affects primarily the gastrointestinal system, and can be treated successfully with antibiotics.

Zollinger-Ellison syndrome

In Zollinger-Ellison syndrome, tumors in the pancreas or duodenum secrete a hormone called gastrin that leads to excessive stomach acid and ulcers.

June 11, 2013