When one or more of a person's toes starts to look blue or purple, doctors call it blue toe syndrome.

There are several triggers, most of which relate to the circulatory system.

This article explains what blue toe syndrome is, what it feels like, its causes, and how doctors treat it.

It will also explore the possible complications of blue toe syndrome and when to see a doctor.

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Blue toe syndrome can cause muscle pain in the legs, as well as severe pain in the foot.

Doctors sometimes call it occlusive vasculopathy or trash foot. Blue toe syndrome is a form of acute digital ischemia. This means it occurs when the toes do not get enough blood.

A person's blood carries oxygen from the lungs to every part of their body. Each cell needs oxygen to repair itself and multiply. The blood also brings cells all the nutrients they need and carries away waste products.

Not getting enough blood damages cells and the tissues they make up. This can cause the tissue to change color — usually blue or purple. When this happens to the toes, doctors call it blue toe syndrome.

Some people with this condition have just one discolored toe on one foot. Others might have discolored toes on both feet.

Some people will find that the toes go back to their normal color when they put pressure on the skin or when they elevate their foot.

As well as blue or purple toes, someone with blue toe syndrome might have:

  • foot pain, sometimes severe
  • muscle pain in the legs
  • ulcers on the feet
  • nodules or lesions on the feet
  • bruising

Blue toe syndrome occurs when a blockage in the small blood vessels in the foot stops the tissues from getting enough blood. Several conditions can cause blue toe syndrome.

Atherosclerosis

Cholesterol is a waxy substance that the body uses to make hormones, vitamin D, and other substances to help food digestion. The body makes all the cholesterol it needs, but people also consume it in foods that include eggs, meat, and cheese.

When there is too much cholesterol in the blood, it can mix with other substances to form plaque. When this plaque sticks to the walls of the arteries, it makes them narrower, causing atherosclerosis. Plaque can also block the arteries.

Embolism

An embolism is when something blocks a blood vessel. Sometimes, pieces of plaque can break away from the artery walls and travel around the body in the bloodstream until they get stuck. The same can happen with blood clots.

Embolisms can occur spontaneously, or an angiogram, vascular surgery, medication, or renal failure might cause it.

Angiogram

An angiogram is a medical procedure. Doctors use it to find and treat blockages and atherosclerosis in the blood vessels.

Doctors place a needle into an artery at the groin, then thread thin tubes called catheters through the arterial system. The team will take X-ray images of the person as they inject a contrast agent into the bloodstream. This substance makes any blockages or other issues easy to spot.

According to researchers, the procedure can sometimes knock a piece of plaque off the artery walls, which can lead to blue toe syndrome.

Vascular surgery

Vascular surgery means any operation on the vascular system. This system includes the arteries, veins, and lymphatic system.

Embolisms are a potential complication of vascular surgery. A piece of plaque, a blood clot, or another particle can circulate in the blood until it gets stuck in a blood vessel. When this occurs in the foot, it can result in blue toe syndrome.

Medication

According to the European Society of Cardiology, medicines designed to thin the blood or treat blood clots can also cause blue toe syndrome. Recreational drugs, such as cocaine, can also trigger the condition.

Renal failure

The kidneys have several roles within a person's body:

  • cleaning waste products from the blood and eliminating them in the urine
  • making sure the blood has the balance of nutrients that cells need — these include sodium, potassium, and calcium
  • producing hormones that control blood pressure and red blood cells

When the kidneys cannot function properly, it is known as renal failure. According to the European Society of Cardiology, this condition can lead to blue toe syndrome

Treatments aim to restore blood flow to the toes. Depending on the cause of the problem, doctors might suggest the following options.

Stenting

A vascular surgeon inserts a mesh tube, known as a stent, into the affected blood vessel. This holds the vessel open so the blood can get through.

Bypass surgery

A vascular surgeon takes a healthy blood vessel from another part of the body and creates a bypass around the blockage.

Doctors usually also advise people to:

  • rest
  • keep warm
  • drink plenty of fluids

Doctors will usually use ultrasound or angiogram to diagnose blue toe syndrome and discover where the blockage is.

If doctors do not restore blood flow to the foot, the tissues can die permanently. Experts call this gangrene. Symptoms include:

  • blue or black skin — appearance can vary with darker or lighter skin
  • pain
  • numbness
  • sores with a foul-smelling discharge

Gangrene is serious, but it is usually treatable with surgery, antibiotics, and oxygen therapy.

However, in severe cases, doctors may need to amputate the affected toes.

Anyone who thinks they have developed blue toe syndrome should speak to a doctor as soon as possible. People who suspect they have gangrene should seek emergency medical attention.

Mild cases of blue toe syndrome are usually easy to treat, but more severe cases can lead to other problems.

The outlook tends to depend on the underlying issue. For example, renal failure can have long-term effects. Also, plaque fragments can block other blood vessels, which affects other parts of the body, including the organs.

Prevention focuses on keeping the heart and the vascular system as healthy as possible. This includes:

  • avoiding smoking
  • keeping active
  • maintaining a moderate weight
  • eating a balanced diet and avoiding foods that are high in cholesterol
  • limiting alcohol intake

Restricted blood supply to the feet can cause blue toe syndrome. This might occur when too much plaque sticks to the inside of arteries, or when a plaque fragment or a blood clot blocks a blood vessel in the foot.

An angiogram, vascular surgery, certain drugs, and renal failure can all cause blue toe syndrome.

To treat the problem, doctors need to restore the blood supply to the feet. Without successful treatment, this condition can lead to gangrene or even amputation.

The best way to avoid blue toe syndrome is to keep the heart and vascular system healthy.