An allergy is a reaction in the body to a normally harmless substance. Usually the immune system functions as the body's defense against invading bacteria and viruses. In most allergic reactions, the immune system is responding to a false alarm.

The word arthritis is used to describe more than 100 different conditions that cause pain, stiffness, and swelling in the joints. There are two main types of arthritis: inflammatory and noninflammatory.

Asthma interferes with normal breathing by narrowing the airways that are within the lungs and that lead to the lungs. This can happen when the muscles around the airways tighten, when there is inflammation and swelling of the airway's lining, or when extra mucus is produced.

Back pain can be caused by inflammation of joints, muscles, or ligaments. Poor posture, obesity, or lifting something the wrong way can cause back pain. Pain also can develop after you sit or stand too long or when you are under physical or mental stress.

Several conditions of the reproductive organs may cause pain, irritation, or other symptoms. Because some of these conditions could lead to infertility or present a serious health risk, all women should become familiar with these conditions and know how to prevent them.

Most women have spotting (light bleeding), breakthrough bleeding (heavier bleeding), or irregular periods at some point in their lives. Spotting or breakthrough bleeding between periods usually lasts 1 or 2 days.

Breast cancer is the most common cancer among women, except for nonmelanoma skin cancer, and the second most common cause of cancer death in American women (lung cancer is the most common cause).

Many symptoms that indicate cancer may be signs of a less serious illness. But the earlier that cancer is detected, the easier it is to treat.

Cervical cancer screening should begin approximately three years after a woman begins having vaginal intercourse, but no later than 21 years of age. Screening should be done every year with conventional Pap tests or every two years using liquid-based Pap tests.

According to the American Cancer Society, an estimated 3,710 women will die from cervical cancer in the United States during 2005. Death rates are dropping, though, because more women are being screened for it. To learn more about cervical cancer and prevention, take this quiz.

Chlamydia infection is a very common STD. Because most people do not have symptoms, chlamydia may not be noticed until it causes severe problems. Left untreated, this STD can cause women and men to become sterile.

Cancers of the colon and rectum together are among the most common cancers affecting Americans, according to the NCI. They occur most often in people over 50 years old. Test your knowledge of colorectal cancer by taking this quiz.

When you have hypothyroidism, your thyroid gland doesn’t produce enough hormone. With hyperthyroidism, the thyroid gland produces too much hormone. A goiter is the enlargement of the thyroid gland.

PMS symptoms occur one to two weeks before your period and may be severe enough to interfere with your normal daily activities.

The most common form of heart disease is atherosclerosis, or hardening of the arteries. Cholesterol joins with calcium and scar tissue and builds up in the arteries. When cholesterol levels are too high, the circulatory system becomes choked—and the result is a dam of plaque that narrows the channels the blood flows through.

More than 18 million people in the United States suffer from depression. About twice as many women as men suffer from this medical condition. Major depression is a whole-body illness that affects a person's body, feelings, thoughts, and behavior.

If you have diabetes, you are two to four times more likely to have heart disease than someone without diabetes. You can control your health risks by making some changes in your life.

Eating disorders, in which food becomes not a source of nutrition but an enemy to be fought or an object of obsession, are most common among middle-class and upper-middle-class women. Approximately 1 in 10 people with eating disorders will die as a result of the condition, either by suicide or a heart attack due to starvation.

Endometriosis is a disease in which tissue from the lining of the uterus moves through the fallopian tubes and attaches to the ovaries, pelvis, bladder, or other areas. Normally the lining of the uterus comes out every month when a woman has her period. With endometriosis, however, some of this tissue does not leave the body.

When sleep and rest do not help ease fatigue, your body is sending you a signal that something else may be wrong.

GERD occurs when the muscle connecting the esophagus with the stomach weakens or does not work properly. As a result, the muscle cannot keep the contents of the stomach from going up into the esophagus.

About 3 to 5 percent of pregnant women who have never had elevated blood glucose levels develop gestational diabetes, a form of diabetes that occurs only during pregnancy. It usually occurs after 20 weeks.

Gonorrhea is a bacterial infection that is transmitted sexually. Many women and some men who have gonorrhea do not have any signs or symptoms. If not treated, gonorrhea can cause swollen and painful joints and permanent damage to your reproductive organs.

The most common warning signals of a heart attack are uncomfortable pressure, fullness, squeezing, tightness, heaviness, or pain in the center of the chest lasting more than a few minutes;pain spreading to the shoulders, neck, arms, or jaw; or chest discomfort with lightheadedness, fainting, sweating, nausea, or shortness of breath.

Hemorrhoids are swollen blood vessels in the anal canal and lower rectum. They are a common cause of itching and rectal bleeding, especially during bowel movements. People with hemorrhoids may notice bright red blood on the toilet tissue or on the stool itself.

If you have herpes, you’re not alone. Millions of Americans have it. Herpes has no cure. But you can control it and learn how to protect yourself and others from outbreaks.

There is no cure for high blood pressure, but it can be controlled. High blood pressure is one of the three major controllable risk factors for cardiovascular disease. The risk relates not only to how high your blood pressure is, but also to how long it has been raised.

High blood cholesterol is one of the major risk factors for heart attack, the leading cause of death in America. Cholesterol is a waxy substance your body produces to help it function properly. Because your liver makes all the cholesterol your body needs, you don't need to consume additional cholesterol.

For most people, lupus is a mild disease that strikes just a few organs. For others, it can cause serious, even life-threatening problems.

Infertility affects more than five million people of childbearing age in the United States. It can be caused by a woman's failure to ovulate or blocked fallopian tubes or a man's low sperm count, among many other factors.

In most cases, lupus involves a malfunction of antibodies - the substances that destroy viruses, bacteria and other foreign invaders. The antibodies lose their ability to tell the difference between attacking microorganisms and the patient's own cells and tissues.

One type of painful period seems to run in families. Researchers in the 1970s and 1980s discovered higher than average levels of prostaglandin -- fatty acids in the body that act much like hormones -- in the menstrual fluid of women who suffered from cramps.

With a migraine, you may have nausea and vomiting and be sensitive to light and sound. You may also have warning signs, such as flashing lights or loss of vision, before the pain starts. Cluster headaches recur in groups for days, weeks, or months.

For most women, the first thing to come to mind when a menstrual period is missed is pregnancy. Although pregnancy is a common cause of missed periods, there are many other factors that can cause a woman not to menstruate

Multiple sclerosis is a chronic, progressive autoimmune disease of the central nervous system (brain, brainstem and spinal cord).

Multiple sclerosis is a disease of the central nervous system, the brain and spinal cord. Its symptoms can range from benign to severe. Find out more about this mysterious illness by taking this quiz.

In recent years, obesity has increased in every state of the United States. Men and women of all races, ages, and education levels weigh more than ever before.

Osteoporosis means "porous bone." It means that your bones are thinner and weaker than they should be. Osteoporosis is the leading cause of fractures in older adults and is most common in people older than 70 and in women who have gone through menopause.

Ovarian cancer is the fifth most common cancer among American women (excluding nonmelanoma skin cancer) and the fourth leading cause of cancer deaths among women. Each year, over 25,000 new cases of the disease are diagnosed in this country, while 16,000 women die from it. It is one of the most lethal cancers affecting women.

Because a cyst may occasionally indicate a more serious condition, see your health care provider if you have abdominal pain, pain during intercourse, swelling in the abdomen, or irregular or unusually heavy periods.

Pelvic inflammatory disease occurs when certain bacteria enter the body. Bacteria can enter the body during childbirth or through procedures such as insertion of an intrauterine device.

It's estimated that PMS affects 70 to 80 percent of women in their childbearing years; 30 to 40 percent of women have symptoms severe enough to interfere with daily activities, and 5 to 10 percent have symptoms so severe they're considered disabling.

Some pregnant women are chronic hypertension sufferers, meaning they have the condition before they become pregnant. Others develop gestational hypertension during pregnancy. Still others develop a hypertensive disorder called preeclampsia.

For most women, a lot of concerns surround a pregnancy. If you're thinking about having a baby, you're better off addressing these issues even before you get pregnant. Failing that, you should address them as soon as you learn you're pregnant.

You could have a very healthy pregnancy and still experience any number of discomforts. These discomforts are caused by the changes that pregnancy brings about in your body. Most don't require treatment, but in many cases there are a few simple things you can do to help make matters better.

Avoid using douches (unless recommended by your health care provider), vaginal sprays, scented toilet paper, or scented tampons. They contain chemicals that can irritate your vagina.

Since we first began hearing about the acquired immunodeficiency syndrome (AIDS) epidemic in the mid 1980s, many people seem to have forgotten that other sexually transmitted diseases (STDs) are still common. Diseases such as syphilis, gonorrhea, genital herpes, hepatitis B, and chlamydia also pose serious health risks.

The more you regularly rely on something external to lift you up, relax you, or help you feel better, the closer you move toward addiction. If you decide you are on the path to addiction, you can take action to keep it under control or find caring people to help you.

Sinus headaches are caused by colds or allergies that make the nasal passages inflamed or infected. The pain most often gets worse in the afternoon and evening. You may also run a fever.

Sleep apnea is a disorder in which breathing stops and starts during sleep. More than half of all cases are diagnosed in people age 40 or older. Sleep apnea is more common in men than women.

Snoring can be caused by one factor or by many, depending on the individual. And, it can be it's own problem or indicate other medical conditions, some of them serious. The list of causes and aggravating factors is a lengthy one.

If we really had no stress -- no competition, no risks to take, no inspiration to try a little harder -- we would be completely bored. It's when the challenges start to pile up that we can lose our ability to effectively deal with stress.

When someone has a stroke, the blood flow to part of the brain stops or is dramatically reduced. Stroke is a leading cause of impairment in older adults. It is the third leading cause of death in the United States.

People don’t talk as much about syphilis today as they did in the past. But people still become infected with syphilis, and it can cause very serious problems.

Tension headaches cause a dull, steady pain on both sides of the head and in the neck and the back of the head. The eyes may also feel tired. Tension headache can be caused by lack of sleep, poor posture, eyestrain, stress, and other factors.

TSS was identified during the early 1980s, when a large number of cases occurred in women who were using highly absorbent tampons. Today, TSS associated with menstruation is relatively rare.

Treatment includes IV antibiotics (medications that help stop infections). If complications develop, other specialized treatments may be needed. Early treatment gives the best chance of a happy outcome.

Anorexia nervosa is an eating disorder that mainly affects young women. It can threaten your health, your well being, and even your life. Much about anorexia isn’t fully understood. But it can be treated.

Bulimia nervosa is a disorder in which food intake gets out of control. Having this eating disorder is nothing to be ashamed of. Talk to your doctor or another person you trust. You may find it’s a relief just to tell someone.

Fibromyalgia (FM) is a complex, often misunderstood illness. Its symptoms are chronic pain, sleep problems, and fatigue. There’s no known cure for the condition, but symptoms can be eased through lifestyle changes and possibly medication.

A person with HIV can look and feel perfectly healthy. But that person can give HIV to others as soon as he or she is infected with the virus.

Miscarriage is common, but finding its cause may not be easy. If a cause can be found, it’s likely to be a problem with the baby or the structure of the uterus.

You’ve just had a baby. You know you should be excited and happy. But instead you find yourself crying for no reason. You feel sad, tired, and hopeless most of the time. You may even feel ashamed or guilty.

Urinary incontinence is the inability to control leakage of urine. It's one of those embarrassing problems people don't like to talk about -- even with their doctors. But there is help for incontinence. In most cases the problem is treatable.

A urinary tract infection (UTI) is usually casued by bacteria that normally are found in the digestive tract or vagina. The bacteria usually enter the through the urethera and can travel to the bladder, causing a bladder infection. But, If the infection is not treated right away, it may move to the kidneys, causing an infection called pyelonephritis.

Women can get different kinds of urinary tract infections (UTIs). Knowing which kind of infection you have may help you prevent future UTIs.

Many women develop uterine fibroids — tumors that grow in the uterine wall or cavity — at some time in their lives. In fact, it's one of the most common medical conditions affecting women. Fortunately, fibroids are almost always non-cancerous.

Although makers of feminine hygiene sprays and douches would like you to believe otherwise, a healthy vagina cleans itself naturally. A clear or opaque vaginal discharge is part of this cleansing process.

Most breast conditions are noncancerous. But if you notice any breast changes that aren’t normal for you, see your healthcare provider.

Do your breasts ever feel “lumpy,” sore, or tender? If so, you may have fibrocystic breasts. This is a very common condition. It is not a disease, and it is not cancer.

The innner lining is the most common place in the uterus for cancer to begin. Cancer can interfere with the working of the uterus and may invade nearby organs. Endometrial cancer may also spread to other parts of the body. This spread is called metastasis. The more cancer spreads, the harder it is to treat.

In rare cases, a woman who has group B strep can infect her baby during the birth. Infection can cause serious illness in the newborn.

Interstitial cystitis (IC) is a chronic and painful condition of the bladder. People with IC have a bladder wall that is tender and easily irritated, leading to uncomfortable symptoms. Although IC currently has no cure, the symptoms can be managed to help you feel better and live more comfortably.

Pelvic organ prolapse is when one or more of the organs inside the pelvis (found between the waist and thighs), slip from their normal positions. Normally, muscles and tissues in the pelvic region support the pelvic organs and hold them in place.

Polycystic ovary syndrome (PCOS) causes harmless cysts in the ovaries and also causes other symptoms. PCOS is caused by certain hormones being out of balance.