Unexplained Bruises: Causes on Legs, Thighs, Stomach, Arms, Breast & Back

It is normal to find a mild blood clot under your skin accompanied by skin discoloration if you had a fall or got injured. However, you can get worried when you get bruises (purple or red inflammation patches on skin) for no reason.

It even gets worse if the unexplained bruising occurs recurrently on your stomach, arms, thighs and skin on thighs.

But what causes it?

In some cases, mysterious bruising may be a sign of an underlying health condition that may need proper diagnosis and medical attention.Unexplained bruises on thighs, legs, stomach and breast

In other cases, it is nothing but minor injuries that went unnoticed on your stomach, arms, legs, feet etc. that are the reason behind the bruising. Below, we have discussed the possible reasons and what to do or when to see a doctor.



As already noted, unexplained bruises may or may be not be an indication of a more serious underlying problem.

Here is an insight into some of the most common causes on numerous parts of the body including feet, legs, thighs, arms, stomach, arms and breasts.

Bruising occurs when factors such as trauma, strenuous activity, and injury to soft tissues cause blood capillaries located beneath the surface of the skin to rupture and leak blood into the surrounding soft tissues. Bruising manifest itself as skin discolorations that range in color from dark red to purple and black-blue.

Such unexplained bruises can cause the affected area to swell, feel tender, or even have some pain, e.g painful bruised ribs.

They generally heal over a time span of 2-4 weeks during which the leaked blood is reabsorbed back into the body.

As this happens, the bruises change to a variety of colors ranging from yellowish green to brown, blue-black, and reddish blue.

Some of the common causes of unexplained bruises are:

1. Injuries or strenuous physical activities like running

Unexplained bruising could be the result of some seemingly minor (or even undetected) injuries. It at times take a few days for the blood to rise close to the skin surface which might make you not even know what caused the bruises.

Strenuous physical activities can also result in damage to blood vessels leading to internal bleeding that show as unexplained bruises.

2. Sunburn

The sun’s Ultraviolet radiation has far reaching consequences on the skin. It not only causes sunburn but also damages the skin making it particularly prone to bruising.

3. Side effect of some medications

There are numerous medications which are known to affect the blood’s ability to clot. For example, aspirin and anti-inflammatory medications such as ibuprofen affect the blood platelet’s function leading to easy bruising.

Other medications such as corticosteroids and birth control pills often cause inflammation of blood vessels sometimes resulting in leakage of blood which manifests itself as bruises.

4. Aging and skin bruises

Unexplained bruising could as well be a result of the natural aging process.  The skin’s ability to produce collagen, an important component of the skin, declines with age.

The skin also loses most of its underlying fatty tissues which provide a cushioning effect to blood vessels. As a result the skin becomes particularly prone to bruising even from insignificant trauma.

5. Vitamin deficiency (vitamin B12, K and C)

Deficiency of vitamin B12, C, and K could also cause unexplained bruises on the skin.

These are important co-factors for various body processes and their presence in inadequate amounts often causes tissues and blood vessels to become weak and more susceptible to bruises.

6. Low or reduced body fat

Body fats provide the skin with a natural cushion against trauma. In that regards, people with thin skin (low fat amounts) are at higher risk of bruising.

People who have undergone a quick weight loss plan could also experience unexplained bruises for the same reason.

7. Diabetes causes bruising

Long time diabetes is often associated with vascular problems and easy bruising. Acanthosis nigricans, a condition characterized by dark colored bruises around the neck is one of the common warning signs of diabetes.

8. Blood diseases

Several blood related conditions and diseases are also known to cause unexplained bruises.

Some of them are leukemia, hemophilia, sepsis, thrombocytopenia, and Hodgkin’s disease. If you suspect any of these conditions, it is advisable to seek prompt medical attention.

9. Grave’s disease

This condition is usually caused by an overactive thyroid, leading to altered body’s physiology.

People suffering from Grave’s disease tend to lose weight and develop thin skin with weak blood capillaries which then makes the skin to bruise easily.

Bruising on legs, feet and knees for no reason

What areas of the body get bruises for no reason? “This morning I noticed several dark red bruises from knee downward to the shin of the leg and feet. They are not painful but some of them seem to be swollen. Does it mean that I have a serious medical condition?” Marylyn, 65 years old mother

Unexplained bruises on the legs, foot or knees as Marylyn describes here is not necessarily a cause for concern.

The legs are particularly prone to bruising compared to other areas of the body and because bruises often take some days to become visible, it can be easy to forget a minor injury that could be to blame for it.

Older people are also at higher risk of bruising since their skin is often more fragile than that of the younger adults due to lowered fat deposits beneath the skin and reduced ability of the skin to produce collagen.

Bruising is especially common among individuals aged above 60 as Gary Goldenberg, MD, assistant professor of dermatology at the Mt. Sinai Hospital points out.

If you have been taking aspirin, anti-inflammatory drugs (ibuprofen in particular) or corticosteroids (e.g. to treat asthma or eczema), then they could be the underlying causes for the unexplained bruising.

The former have a thinning effect on blood making it less effective in clotting while the latter often causes an inflammation of blood vessels leading to leakage.

Most bruises go away on their own in 2-4 weeks. You may however want to undertake a home treatment remedies for bruises to speed up healing and relieve the symptoms e.g. swelling, pain, etc. Your best course of action is to applya cold compress over the first 2 days and follow it up with warm compresses thereafter.

Cold compresses to relieve bruising

For cold compress, wrap an ice pack in a towel or soak a cloth or flannel in cold water and then place it on the bruised area for about 10 minutes. Avoid placing ice pack directly on the skin as this is too cold and can worsen the symptoms especially pain.

As for warm compress, simply place a cloth in warm water and let the heat dissipate out on the affected area of skin for 10 minutes or so several times daily.

If the bruises are still there a couple weeks down the line even with the above home care measures, see your doctor.

You could be dealing with a more serious medical condition or disease that is disrupting your circulation, weakening your blood capillaries, or affecting your blood’s ability to clot. If the bruises also recur every now and then, it may also be worth your time to go see your doctor.

Mysterious clots on thighs

“I am a 30 years old mother of three. For the past one and a half months, some purple colored bruises have been appearing on my thighs. I have had around 3 consecutive sets of bruises on my thighs. There is no history of blood disorders in my family and a blood analysis at my doctor’s clinic revealed nothing. Any clue what this could be?” Alicia

While unexplained bruises are often a sign of serious blood disorders such as anemia and leukemia among others, it may as well be caused by other factors including:

Exercise and strenuous activity: These can cause microscopic tears in blood capillaries leading to internal bleeding that manifests itself as bruises.

Injury: Often what we perceive as unexplained bruises on thighs is a result of bumps into bedpostswithout knowing or small injuries that are already forgotten by the time a bruise becomes visible on the surface of the skin; usually after a few days.

Women are especially more prone to bruising than men and even minimal traumas or injuries to their skin especially on the thighs, upper arms and buttocks can cause bruises. It could be that you are just clumsy for lack of better words.

Medications and supplements: Some medications could also be to blame. Contraceptives pills may be to blame and so can some food supplements such as ginkgo, fish oil and garlic. The potential effects of some drugs on skin vessels is explained in more details in a previous section of this article.

Nutritional deficiency of vitamin C, B12, K, and folic acid could also be the underlying cause of those unexplained bruises on thighs. Taking foods rich in these essential nutrients could help.

On armS

“In the last couple weeks I have been getting lots of unexplained bruises on my arms. Someone told me that it could be a symptom of diabetes which happens to run in our family and I am very worried, being only 19 years old. Does bruising on the arms have any linkage to diabetes?” Amery

Bruising easily around arms may occur for many reasons but diabetes is an unlikely culprit in your particular case.

Bruising and diabetes join hands so to speak in a condition known as acanthosis  nigricans which manifests itself as brown or black patches of skin discoloration in body folds and creases particularly in the armpits and the back of the neck.

This happens when insulin spills over into the skin as a result of insulin resistance typically associated with Type II diabetes. You can always watch for these other symptoms to rule out diabetes: increased thirst, more frequent urination, extreme hunger, fatigue, weight loss, blurred vision, and frequent infections.

Unlike acanthosis nigricans, bruises occur when there is internal bleeding in the skin as a result of injury or trauma.

Usual suspects for unexplained bruising (keeping in mind Amery’s age) are:

  • Rigorous exercising e.g. athletics and weightlifting which often causes breakage of blood vessels
  • Vitamin C, B12, K and folic acid deficiency
  • Side effect of medications and supplements. Aspirin, warfarin, corticosteroids (e.g. prednisone), anti-inflammatory drugs (ibuprofen), and dietary supplements the likes of fish oil, ginger, garlic, and ginkgo may cause unexplained bruising.
  • A blood clotting or bleeding disorder e.g. leukemia
  • Liver disease e.g. Primary biliary cirrhosis
  • Inflammation of blood vessels

You should seek medical attention if the bruises are particularly large or too frequent, are accompanied by bleeding gums or prolonged menstrual periods, or take more than have not shown any signs of improvement after a couple weeks or have not yet healed four weeks down the line.

On Breast and Stomach

“I am scared about this large bruises on my breasts and stomach. They just started out of nowhere and began with an urge to scratch. I am in perfect health and have not had any skin issues before. Is this serious problem and do I need to seek medical mention?” Claire

Unexplained bruises that are accompanied by itching is often a sign of a serious liver condition known as primary biliary cirrhosis. It could as well be the result of a local skin reaction. For instance, some severe hives may cause a color change that looks like alarge bruise.

Your safest course of action would be to go and see your doctor immediately for appropriate diagnosis and treatment.

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