asthma
Asthma is a long-term disease of the lungs. It makes you wheeze, cough and feel short of breath. Asthma attacks are caused by iflammation and narrowing of the airways, which makes it hard for air to pass in and out of the lungs.

emphysema
Emphysema is a long-term disease of the lungs. The walls of the air sacs (alveoli) in the lungs become thin and less elastic. This makes it harder for oxygen to get in your blood and carbon dioxide to get out of your body. It makes you cough and feel short of breath. Smoking is the most common cause of emphysema.

flu
The flu is a bad infection that gives you a headache, sore throat, aching joints and a fever. Flu is caused by infection with a virus called influenza.

immune system
The immune system is made up of the parts of the body that are devoted to fighting infection. The body is constantly being threatened by infections from things like bacteria, viruses and parasites. The immune system fights these infections in different ways. At the microscopic level, the immune system uses antibodies and white blood cells, which travel in the blood and target infectious agents, such as bacteria. These microscopic parts of the immune system either kill the infectious agent directly, or take it to other parts of the body, like the spleen, where it can be dealt with. The lymph nodes are another important part of the immune system. Within them, white blood cells filter through the foreign material that has entered the blood, to see if there are any infections. When you have a swollen gland during a cold, this is actually a lymph node that is reacting to the infection. Unfortunately, it is possible for the immune system to become confused and to use its destructive powers to target healthy parts of the body. Diseases that result from this type of situation are called autoimmune diseases.

diabetes
Diabetes is a condition that causes too much sugar to circulate in your blood. It happens when your body stops making a hormone called insulin (type 1 diabetes) or when insulin stops working (type 2 diabetes).

heart disease
You get heart disease when your heart isn't able to pump blood as well as it should. This can happen for a variety of reasons.

sickle cell disease
Sickle cell disease is a blood disorder that runs in families. Under certain conditions, the red blood cells of people with this disease change shape to look like a sickle. This causes a lot of pain and a range of other symptoms, including infections in the lungs.

AIDS
AIDS stands for acquired immunodeficiency syndrome. People who are infected with the human immunodeficiency virus (HIV) get AIDS when the virus has destroyed most of their immune system. When people have AIDS, their body isn't able to fight infections. So even common infections, such as colds, can cause serious problems.

leukemia
Leukemia is a type of cancer that affects the body's production of white blood cells. White blood cells are important for fighting infections. So, if you have leukemia you are more likely to catch an infectious disease.

chemotherapy
Chemotherapy is the use of chemicals or drugs to treat or prevent disease, usually cancer.

high temperature
A high temperature is a general sign that there is an infection or inflammation in your body. Temperatures vary, but anything over about 100 degrees Fahrenheit is considered high.

stethoscope
A stethoscope is a tool doctors use to listen to people's bodies. One part of the stethoscope is a disc (called the bell), which doctors put over a part of someone's body (like their heart or a vein). The bell is connected to ear pieces, which the doctors put in their ears so they can listen to sounds that come from that part of the person's body.

inflammation
If your skin or some other part of your body becomes red, swollen, hot or sore, we say it is inflamed. It means that your body is trying to protect you from germs, from something in your body tissues that can hurt you (like a thorn or sliver), or from things that cause allergies (allergens). Inflammation is part of the way the body heals an infection or injury.

X-ray
X-rays are pictures taken of the inside of your body. They are done by passing very small amounts of radiation through your body and onto film. X-rays can also be used as a treatment, such as in radiation therapy for cancer.

white blood cells
White blood cells are the cells in your blood that help your body fight infections. The other cells in your blood, red blood cells, carry oxygen around your body.

immune system
The immune system is made up of the parts of the body that are devoted to fighting infection. The body is constantly being threatened by infections from things like bacteria, viruses and parasites. The immune system fights these infections in different ways. At the microscopic level, the immune system uses antibodies and white blood cells, which travel in the blood and target infectious agents, such as bacteria. These microscopic parts of the immune system either kill the infectious agent directly, or take it to other parts of the body, like the spleen, where it can be dealt with. The lymph nodes are another important part of the immune system. Within them, white blood cells filter through the foreign material that has entered the blood, to see if there are any infections. When you have a swollen gland during a cold, this is actually a lymph node that is reacting to the infection. Unfortunately, it is possible for the immune system to become confused and to use its destructive powers to target healthy parts of the body. Diseases that result from this type of situation are called autoimmune diseases.