“Vaso” actually means blood vessel. Vasoconstriction is narrowing or constriction of the blood vessels. It happens when smooth muscles in blood vessel walls tighten. This makes the blood vessel opening smaller. Vasoconstriction may also be called vasospasm.
Vasoconstriction is a normal process. It helps keep your body in healthy balance.
Vasoconstriction may occur to:
- stabilize blood pressure or raise blood pressure
- reduce loss of body heat in cold temperatures
- control how blood is distributed throughout your body
- send more nutrients and oxygen to organs that need them
- protect your body against blood and fluid loss
On the other hand, abnormal vasoconstriction can trigger some health conditions. This includes high blood pressure and headache pain. In some cases, too much blood vessel narrowing may be a side effect of drugs and foods, such as caffeine and salt.
Read on to learn about the causes of vasoconstriction and how it affects your body.
Vasoconstriction reduces the volume or space inside affected blood vessels. When blood vessel volume is lowered, blood flow is also reduced. At the same time, the resistance or force of blood flow is raised. This causes higher blood pressure. Untreated high blood pressure (hypertension) can lead to health conditions over time, like vision loss, stroke, or a damaged heart.
The opposite of vasoconstriction is vasodilation. This is when blood vessels relax and widen, increasing blood flow and dropping blood pressure.
Think of vasoconstriction as drinking through a thin straw. It takes more suction force to take a sip. In comparison, vasodilation is like gulping a drink easily and quickly through a wide straw.
Abnormal vasoconstriction may cause or worsen high blood pressure. Chronic high blood pressure can increase your risk of heart disease and stroke. Some health conditions and drugs can cause too much vasoconstriction or make it happen in areas that it shouldn’t, such as parts of the brain.
Foods high in sodium can put stress on your blood vessels, causing them to constrict. If you’re concerned about your blood pressure, avoid or limit the following foods:
- packaged and fast foods
- deli meat
- canned soups
Alcohol can also raise your blood pressure, notes the Mayo Clinic.
Vasoconstriction can both help alleviate and cause migraines and headaches.
When vasoconstriction helps headaches
Enlarged blood vessels in the head can set off migraine or headache pain. Medications to treat this type of pain often work by causing vasoconstriction. This helps the blood vessels constrict and stop excess blood flow.
Some headache and migraine medications contain caffeine for this reason.
When vasoconstriction can cause headaches
On the other hand, too much caffeine can cause excess vasoconstriction in the brain. This may trigger a migraine or headache. The American Migraine Association explains that this may happen because the body becomes dependent on caffeine. Withdrawal symptoms from coffee and headache medications include headache pain, nausea, and fatigue.
Shock is a general term for the body’s response to a number of different emergency conditions. These conditions all cause low blood pressure. The body’s first response is to protect the brain, heart, and lungs. It does this by narrowing the blood vessels in the hands, feet, and limbs.
This emergency vasoconstriction temporarily raises blood pressure. It helps keep blood flowing to your most needed organs — the organs needed for life.
Shock may happen due to:
- allergic reaction (anaphylactic shock)
- septic infection (bacterial, viral, or fungal)
- heart attack
- heart disease
- low blood sugar
- blood clot
- heavy blood loss (internal or external)
- heavy loss of fluids (dehydration, vomiting, diarrhea)
- serious burns
- spine injury
- severe hypothyroidism
Vasoconstrictor or pressor medications help relieve low blood pressure and other symptoms. These drugs may be used to raise blood pressure when someone is in shock, has excessive bleeding, or has a severe allergic reaction.
Other prescription drugs trigger vasoconstriction to help reduce inflammation, swelling, or excess bleeding. For example, a nosebleed may be stopped with a vasoconstrictor drug.
Vasoconstriction medications include:
- alpha-adrenoceptor agonists
- vasopressin analogs
- phenylephrine (Sudafed PE)
- migraine and headache medications (serotonin 5‐hydroxytryptamine agonists or triptans)
Some health conditions and medications can cause abnormal vasoconstriction. This can lead to health problems depending on where this happens and for how long.
Vasoconstriction in the brain or cerebral vasospasm can lead to a stroke or a strokelike injury. This may happen after there’s bleeding in the brain due to a blood vessel rupture or surgery. The blood vessel spasms or narrows to try to save blood. This cuts off the supply of blood and oxygen to a part of the brain.
Symptoms of a cerebral vasospasm stroke include:
- severe headache pain
- dizziness, loss of balance
- numbness or weakness on one side of the face and body
- difficulty speaking
- difficulty seeing in one or both eyes
- difficulty walking
Raynaud’s phenomenon causes some areas of the body, such as the fingers and toes, to feel cold or numb. In this condition, the small arteries that supply blood to these areas spasm or narrow. This limits how much blood can reach these outer areas.
Raynaud’s phenomenon can also affect the nose, lips, ears, and nipples. It can be triggered by being in the cold too often. This may happen to people who work outside in colder regions or who spend a lot of time on an ice rink, such as ice skaters, hockey players, and Zamboni drivers.
This condition isn’t harmful, but it can be uncomfortable. In some cases, Raynaud’s phenomenon may increase the risk of skin infections and slow wound healing in the affected areas. This happens because normal blood flow is needed to carry oxygen, nutrients, and infection-fighting immune cells throughout the body. Vasoconstriction limits blood circulation.
Reversible cerebral vasoconstriction syndrome
Reversible cerebral vasoconstriction syndrome (RCVS) is a range of disorders caused by vasoconstriction in the brain. It’s reversible in most cases. You’ll recover fully within months.
In serious cases, RCVS can lead to stroke. This happens when the blood vessels narrow too much or for too long and cut off blood flow and oxygen to parts of the brain.
RCVS can sometimes occur in babies. It can lead to high blood pressure, headache pain, and stroke. It may be triggered by the side effects of medications. These include chemotherapy drugs for eye and brain cancers in babies and children.
Symptoms of RCVS include:
- sudden, intense headache
- changes in vision
- difficulty speaking
- difficulty understanding speech
- weakness, usually on one side of the body
Smooth muscles — the type of muscle in the blood vessel walls — can’t be controlled voluntarily like the skeletal muscles in your limbs. Blood vessels are automatically controlled by chemical signals in the body that tell the smooth muscles to constrict or dilate (widen).
The nerve chemical messengers and hormones that tell blood vessels to constrict include:
- angiotensin II
Arteries and arterioles (small arteries) have muscular walls. They’re the main blood vessels involved in vasoconstriction. Veins can also narrow. Capillaries are tiny, thin-walled blood vessels that can’t constrict.
Vasoconstriction of the blood vessels is a natural part of your body balancing its systems. Vasoconstriction is needed to help maintain healthy blood flow and keep your body temperature from getting too cold. It can also raise blood pressure when it’s necessary.
Some medications mimic your body’s natural signals to cause vasoconstriction. This can be life-saving. For example, vasoconstriction drugs can stop blood pressure from dropping too low during a serious allergic reaction and reduce blood loss in an injury.
Speak to a healthcare provider if you have questions about your blood pressure, heart rate, or other symptoms like headaches.