What Causes Unexplained Bruising?

Bruising happens when tiny blood vessels under the skin—called capillaries—break due to an impact or pressure, causing blood to leak into the surrounding tissue. This leads to discoloration that changes from red or purple to blue, green, and yellow as the bruise heals. While most bruises are harmless and occur from minor bumps we may not even notice, frequent or unexplained bruising can sometimes signal an underlying health issue. Below are the most common causes, explained in more detail:

1. Vitamin Deficiencies

Certain vitamins play a key role in maintaining strong blood vessels and proper blood clotting. When the body lacks these nutrients, bruising can appear more easily.

• Vitamin C Deficiency (Scurvy):

Vitamin C is essential for producing collagen, a protein that supports blood vessel strength and elasticity. Without enough vitamin C, capillaries become fragile and break easily, resulting in frequent bruises. Individuals may also experience fatigue, irritability, joint pain, and bleeding gums.

• Vitamin K Deficiency:

Vitamin K is crucial for the body’s clotting process. When levels are low, even small injuries can lead to excessive bleeding and unusually large or persistent bruises. This deficiency may occur due to poor diet, digestive issues, or certain medications that interfere with absorption.

2. Blood Disorders

Some conditions affecting the blood’s ability to clot or produce healthy cells can cause unexplained bruising.

• Leukemia:

One of the early warning signs of leukemia—a cancer affecting the blood and bone marrow—is frequent bruising without clear cause. This occurs because the body produces fewer platelets, which are necessary for clotting. Additional symptoms can include fatigue, recurrent infections, weight loss, and tiny red spots on the skin called petechiae.

• Hemophilia:

This inherited disorder prevents blood from clotting normally. Even minor injuries can lead to deep, painful bruises and prolonged bleeding. Hemophilia typically appears in childhood but can also be diagnosed later if symptoms are mild.

3. Anemia

Low red blood cell or iron levels can weaken the body in various ways, including making bruising more likely.

• Iron Deficiency Anemia:

Iron helps support healthy blood cell production. When iron levels drop, the blood carries less oxygen, and the walls of blood vessels can become more fragile. This results in bruises forming more easily, even from small bumps. Other signs include tiredness, pale skin, headaches, and feeling faint.

4. Certain Medications

Some medications affect blood clotting or skin strength, increasing the risk of bruising.

• Blood Thinners:

Drugs like aspirin, warfarin, heparin, and some herbal supplements (such as ginkgo biloba) make it harder for blood to clot. This means that even mild pressure can leave noticeable bruises.

• Steroids:

Long-term use of corticosteroids can thin the skin and reduce the protective tissue layer beneath it, causing bruises to appear more frequently.

5. Aging and Fragile Skin

As people grow older, the skin naturally becomes thinner and loses collagen, elasticity, and the protective fatty layer beneath the surface. This makes blood vessels more exposed and vulnerable to damage from everyday activities. Elderly individuals may bruise from simple tasks like leaning on furniture, carrying bags, or brushing against hard surfaces.

If unexplained bruising becomes frequent, painful, or appears with other symptoms—such as fatigue, bleeding gums, or sudden weight loss—it’s important to seek medical evaluation. Many causes are harmless, but some require treatment to prevent complications.