Random bruising on your legs (as well as on other body parts) can cause unsightly skin discoloration as a result of a mild trauma or injury. Many people find that they have unexplained bruising on legs and want to know what causes bruises to appear for no apparent reason. Some people also bruise more easily than others and a seemingly insignificant knock may leave a black and blue dark patch on their skin.

Random or unexplained bruising on legs can happen for a number of reasons. For example, being in the sun too long, aging, or a vitamin deficiency can weaken small blood vessels near the skin’s surface. This can result in bruising easily on your legs or other areas of your body. Sometimes, bruising without an injury could be a sign of a serious underlying medical condition like diabetes, a blood clotting disorder, or an autoimmune disease.

In this article, you will find out what could be causing random bruising on your legs and other body parts, and in some cases, how to get rid of the bruise quickly. First of all, let’s look at what bruises are and what is the main cause of random bruising.

What Is a Bruise?

It’s very rare to have spontaneous bruising without any reason. People who are prone to bruising may not remember a minor trauma and assume that the bruise has appeared out of nowhere. Most bruising occurs as a result of some kind of injury.

Dr. John Cunha on eMedicineHealth explains that discoloration on the skin is caused by tiny blood vessels breaking under the skin. This causes blood from damaged veins and capillaries to collect near the surface of the skin. A bruise usually starts off as a black and blue patch of skin and gradually turns green or yellow as it heals.¹

You may find that the bruises on your body are painful at first but they may start to itch as they heal. Dr. Cunha says that it will take between one to two weeks for bruises to completely heal.²

Causes of Random or Unexplained Bruising on your Body and Legs

Knowing the reason for the appearance of mysterious bruises can help to prevent them in the future. This can also help you to determine if you should see a doctor about unexplained bruises that have appeared on your body.

Aging

Older people tend to bruise easily because of changes to their skin as they age. Doctors from the Mayo Clinic explain that aging causes the protective fatty layer in the skin to become thinner. This means that elderly people are more prone to random bruising than younger adults.³

According to a report prepared by the University of California, elderly people may also be less stable on their feet and can bump into objects frequently causing accidental bruising. However, the report recommends that any unexplained bruising on an older person be investigated to rule out the possibly of abuse. Authors of the report said that 90% of bruising occurs on the legs and arms and very rarely on the neck, ears, buttocks, or soles of the feet.⁴

Vitamin deficiency

One cause of random bruising on legs or bruises that appear after a minor injury is a vitamin deficiency. For example, a lack of vitamin C can lead to scurvy which causes unexplained bruising and bleeding. Vitamin K is needed to help blood clot properly and prevent random bruising.

The Journal of the American Academy of Dermatology reported that ascorbic acid (vitamin C) helps to strengthen blood vessels and prevent them breaking. Vitamin C supplements are also used to help reduce random bruising in patients suffering from skin diseases that cause bruising.⁵

According to MedlinePlus, vitamin K plays a major role in blood clotting. Vitamin K supplements are often given to prevent unexplained bruising in people who take blood thinning medication.⁶

Vitamin C and K deficiencies can also be responsible for petechial rash or purpura which look like flat tiny red, brown, or purple spots on the skin (petechiae) or larger ones (purpura).

Side effects of some medicines or supplements

Certain medications and supplements can cause the blood to thin and result in random bruising on the body. If you are taking blood-thinning medications, you may find that even a slight knock on your leg or arm can easily cause bruising.

According to doctors from the Mayo Clinic, aspirin, some antibiotics, and anticoagulant medications can cause clotting problems. This can result in random bruising or larger bruises from trauma to the skin.³

Also, supplements like ginkgo biloba, ginger, turmeric, St John’s Wort have blood-thinning properties and may make you bruise easily. Before taking any supplements that thin the blood, you should speak to your health care provider if you are already taking medication to prevent blood clots.

That is one reason why some people shouldn’t take turmeric regularly for medicinal purposes. Ginger should also be used with care if you take medication to thin the blood.

Hereditary conditions

Sometimes unexplained bruising on your legs or body is because of hereditary factors. Dr. William Blahd on WebMD says that if your parents bruised easily, there is a greater chance that random bruising will affect you as well.⁷

Women tend to bruise more easily than men. This is because women have more fragile blood vessels and may bruise more easily on their legs, upper arms, or buttocks. Dr. Blahd says that if you have no other symptoms, then random bruising is nothing to worry about.

Bleeding disorders

Bleeding disorders may cause large bruises to develop without any explanation. For example, hemophilia and Willebrand disease affect the blood’s ability to clot and can cause bleeding and excessive bruising resulting in black or dark skin patches.

However, unexplained bruising by itself isn’t the only symptom of a bleeding disorder. The National Hemophilia Foundation says that along with excessive bruising, hemophiliacs usually have unexplained nosebleeds, extended bleeding from minor cuts and scrapes, and women may have very heavy menstrual periods.⁸

Too much sun

Although being in the sun is necessary to help the body produce vitamin D, too much sun exposure can damage your skin and cause you to bruise easily. Sunburn can take a long time to heal and its effects can be long-lasting.

The website Drugs.com warns that long-term overexposure to the sun’s harmful UV rays can cause the skin to bruise easily on exposed areas. This can even cause permanent discoloration to your skin. If you notice abnormal bleeding under your skin after a sunburn, you should call your doctor for a checkup.⁹

If your skin shows signs of a sunburn, like reddened skin, skin tender to touch, and blisters, you can get relief from sunburn using natural remedies like aloe vera, honey, witch hazel, or oatmeal.

Intensive exercising

Intensive exercising can cause unexplained bruises in the parts of your body under stress. According to Dr. Debra Jaliman on WebMD, vigorous exercise like lifting weights or intensive training can cause tiny tears in blood vessels under the skin.¹⁰

Also runner’s or jogger’s toenail is one of the most common reasons for bruised toenails as the toe pushes against the front of the shoe while running or jogging.

If you notice that you have bruising after working out that is unexplained or the result of an injury, you should follow the “RICE” method to help the bruise heal quicker. The RICE method for getting rid of a bruise is:¹¹

• Rest the injured limb.
• Ice the affected area. Remember that you should not put the ice directly on your skin.
• Compression to prevent swelling and inflammation.
• Elevation to prevent too much blood getting to the affected area.

Diabetes

If you suffer from diabetes, you may notice that you bruise easily and bruises last longer. Random bruising caused by diabetes occurs when the condition affects the blood vessels and causes peripheral vascular disease. Along with frequent unexplained bruising on your legs, diabetes causes increased thirst and urination, weight loss, nausea, and abdominal pain.

According to Dr. Melinda Ratini on WebMD, peripheral vascular disease commonly affects the legs.¹² The journal Physical Therapy says that a complication of diabetes is bruising or injuries that don’t heal.¹³

Unexplained bruising on your legs is one of the signs of advanced diabetes. However, there are early warning signs of diabetes that can indicate you are at risk for developing the disease. If you have diabetes, it’s important to manage it properly. Your doctor may recommend controlling diabetes with diet or prescribe you medication.

Viral infection

Viral infections can also cause random bruising on legs that is unexplained. Some viral infections can cause a condition called thrombocytopenia that affects blood clotting.

According to Dr. Neha Pathak on WebMD, some common viral infections that can cause unexplained bruising are chickenpox, mumps, and rubella. Other medical conditions like HIV, aplastic anemia, or leukemia can also affect blood platelets making it more difficult for blood to clot and lead to unexplained bruising.¹⁴  

Autoimmune disease

Various autoimmune diseases can be a reason why you are bruising easily and can’t find the reason for it. Autoimmune disorders occur when the body produces antibodies that attack its own tissues rather than fight infections.

Some autoimmune diseases that cause unexplained random bruising are:

• Lupus. The American Academy of Family Physicians says that easy bruising and excessive bleeding can be caused by lupus.¹⁵
• Rheumatoid arthritis. Apart from causing bruising in various areas of your body, the journal Annals of Rheumatic Diseases says that very often medications used to treat rheumatoid arthritis cause random bruising.¹⁶
• Vasculitis. Vasculitis is inflammation of the blood vessels and one of its symptoms is bruising. The National Heart, Lung, and Blood Institute says that vasculitis can cause skin changes like purple or red spots, splotches, and bruises.¹⁷

Other Causes of Unexplained Bruising

There are some serious advanced medical conditions that can also cause unexplained bruising on your body. Usually, these diseases are accompanied by other symptoms and random bruising occurs in the later stages of the disease.

Liver disease

Serious liver disease can cause easy bruising because the liver can’t produce enough blood clotting factors.

Dr. Dennis Lee on MedicineNet says that along with random bruises, liver disease can turn the skin yellow and cause all over body itching. Liver disease may also make legs swell and cause intestinal bleeding.¹⁸

Kidney disease

Easy bruising is sometimes a symptom of the late stages of chronic kidney disease.

Dr. Charles Silberberg, says that a person with advanced kidney disease may also have drowsiness, numbness in hands and feet, breath odor, blood in the stool, and/or vomiting in the mornings.¹⁹  

Cancer

Some cancer treatments can affect blood platelets causing easy bruising and bleeding that is difficult to stop. The National Cancer Institute says that chemotherapy can cause random bruising, as well as tiny purple or red spots on your skin.²⁰  

An unexplained bruise on your breast that doesn’t go away could be a sign of inflammatory breast cancer. Other symptoms of inflammatory breast cancer are painful breasts that suddenly swell, itching, and nipple changes or discharge.²¹

Another type of cancer that can cause easy bruising is leukemia. The American Cancer Society says that leukemia can cause a number of symptoms including weight loss, constant tiredness, recurrent infections, and unexplained bleeding.²²  

Although in rare cases random bruising can be a sign of a serious condition, the bruising will be accompanied by many other symptoms. It’s good to remember that in most cases the cause of unexplained bruising is nothing to worry about.

When to See a Doctor

Usually, bruises disappear in about two weeks. According to the NHS website and WebMD, you should see your doctor if you have unexplained bruising along with any of the following symptoms:^{23, 24}

• The bruise doesn’t heal within two weeks.
• You notice bruises on your legs or other areas of your body for no apparent reason.
• You suddenly start to bruise easily.
• You have severe pain in the bruised part of your body.
• There are signs that the bruise has become infected.

Natural Ways to Get Rid of Bruises

There are many natural home remedies you can use to reduce inflammation, relieve pain, and help bruises heal faster. You might have many of these remedies such as tea bags and aloe vera right at your fingertips. I have already mentioned these natural treatments for bruises that are backed by scientific evidence. You can read about these treatments in my article on how to get rid of bruises naturally.