Blood pressure is the force of blood in your arteries when your heart pumps and when it rests, explains the Mayo Clinic. A normal blood pressure, according to the American Heart Association (AHA), is 120/80. This may vary slightly for each person, but a significant or sudden drop in this number can be dangerous, and can have several causes.
Pregnancy
It is normal for a woman's blood pressure to drop during the first 24 weeks of pregnancy due to the circulatory system expanding at a rapid rate to accommodate the fetus, according to the AHA. This affects both the systolic (top) and diastolic (lower) numbers.The Mayo Clinic explains that the systolic number can drop by as much as five to 10 points, while the diastolic number may drop between 10 and 15 points. After delivery, blood pressure typically returns to normal.
Severe Allergic Reactions
A severe allergic reaction known as anaphylaxis tends to occur due to allergies to penicillin, bee stings, latex products and peanuts. These allergies have the potential of being life-threatening. A sudden drop in blood pressure is a major symptom of anaphylaxis, along with swelling of the throat, difficulty breathing and itching.
Dehydration
The AHA and the Mayo Clinic both agree that dehydration can cause low blood pressure. The AHA notes that while dehydration may cause a drop in blood pressure, people should not be quick to consider it a sign of low blood pressure because dehydration can have a number of other causes, including fever, vomiting, severe diarrhea and overuse of water pills.
In some cases, a complication called hypovolemic shock can stem from dehydration. The Mayo Clinic explains that this is a life-threatening condition, and occurs due to a low blood volume in the body, which results in a drop in blood pressure.
Heart Conditions
Certain heart conditions prevent the body from circulating enough blood through the body, causing blood pressure to drop. The more common heart conditions responsible for low blood pressure include heart valve problems, a low heart rate (known also as bradycardia), heart failure and heart attack.
Septicemia
Also known as septic shock, septicemia occurs when bacteria leaves the original infection, usually located in the abdomen, lungs or urinary tract, and finds its way into the bloodstream. The bacteria produces toxins and contaminates the blood vessels, which leads to a significant drop in blood pressure.
