Severe or prolonged stress can affect your health.  Stress can trigger certain illnesses, reduce the body's ability to fight an illness, and make some diseases harder to control. 

Stomachaches - A "stomachache"can occur in your stomach, small intestine, or large intestine.  Stress disrupts the movement of food through the digestive system.  The food may move too quickly or too slowly.  You might experience gas, cramps, diarrhea, or constipation.  Stress also increases the amount of stomach acid.  Doctors used to think that excess acid attacted the lining of the stomach and caused open sores called ulcers.  When medicine was used to kill bacteria, the ulcer healed.  Current thinking is that excess acid makes it more likely that an ulcer will form and makes it more difficult for an ulcer to heal. 

Asthma - Asthma is another illness for which stress can be a trigger.  an asthmatic attack happens when the air passages of the respiratory system narrow, making it difficult to breathe.  During an attack, the person coughs, wheezes, and gasps for air.  These symptoms can usually be controlled by medication that is inhaled.  But it helps if people with asthma recognize which stressors can trigger an attack. 

Headaches - Stress can trigger headaches.  Tensions in the muscles around your scalp, face and neck may produce an aching or pounding sensation in your head.  A type of headache called a migraine begins when blood vessels in the brain and scalp narrow, which limits the supply of oxygen to the brain.  The blood vessels must then open wide to increase the flow of oxygen.  This stretching of the blood vessels causes the painful throbbing of a migraine.  If you suffer from frequent headaches, you may want to keep a diary to determine what factors trigger the onset of a headache.  In addition to stress, certain foods, such as chocolate or large amounts of caffeine, can trigger headaches. 

Lowered Resistance to Disease - The immune system protects your body from disease through a complex process involving many specialized cells.  When speak of fighting off a flu or cold, your immune system does the fighting.  When your immune system functions well, you are better abled to resist some of the illnesses to which you have been exposed.

Scientific research has shown that, during the alarm stage, some of your immune system may function better than usual.  However, prolonged stress can prevent the immune system from functioning well.  If your immune system is weakened, you may develop minor illnesses, such as colds, more often.  For people with diseases such as cancer, a weakened immune system makes it harder to control the disease.

Heart Disease - Some effects of frequent or prolonged stress do not show up until later in life.  Remember that during the alarm stage, your heart beats faster.  Your blood vessels narrow and your blood pressure rises.  Your heart must work harder to keep blood flowing through your body.  Stress that is frequent or prolonged can cause damage to the muscle fibers in the heart.  Because high blood pressure has no obvious symptoms and often goes undetected, it is sometimes called " the silent killer".  Reducing stress is one of the ways that people can lower their blood pressure and reduce the risk of heart disease and stroke.