Frequent leg bruising can result from aging or some medications. It may also occur if you have certain health conditions, including vitamin deficiencies and bleeding disorders.

It can be alarming to see unexplained bruises on your legs or your child’s legs, particularly if you don’t recall an incident that could’ve caused them.

Bruises develop from damage to blood vessels that reside under the skin. This damage causes the blood vessels to leak blood, leading to discoloration of the skin.

Unexplained bruising on the legs can occur in both adults and children due to a variety of factors, including injury, age, an underlying health condition, or even things like medication.

For example, in adults, bruising can occur more easily as we age due to thinning of the skin. Therefore, even a small bump could cause a bruise.

Meanwhile, the specific cause of bruising in children can sometimes be difficult to determine. Children often fall or get bumped when learning to walk or while playing.

Read on to learn more about what can cause unexplained bruising on the legs as well as when you should see your doctor.

What factors affect bruising?

We’re all probably familiar with getting bruises due to injury. Maybe you fell down or bumped into something. There are actually some factors that can cause you to bruise more easily:

  • Age. Older adults bruise more easily due to thinning of the skin and less cushioning from fat.
  • Sex. Women tend to bruise easier than men.
  • Family history. If other people in your family bruise more easily, you may, too.

If you do bruise more easily, a minor bump could lead to a bruise, and you may not remember the injury that caused bruises to appear on your leg.

What else can cause unexplained bruising?

Other factors may cause unexplained leg bruising. Often, these things affect your body’s coagulation process.

Coagulation, or clotting, is your body’s ability to seal a wound and stop bleeding. There are several factors involved in clotting, such as platelets. These cells help your blood clot.

If something is hindering the effectiveness of the clotting process, bruising and bleeding may result. This can happen in a variety of ways:

  • Platelets or other clotting factors aren’t functioning properly.
  • There aren’t enough platelets or other clotting factors being produced.
  • Platelets or clotting factors are being destroyed.
  • Some clotting components are absent (inherited bleeding disorders).

Keep in mind bruising on the legs is a very common occurrence and can happen quite easily. By itself, it’s usually not a sign of an underlying health condition. You’d most likely have bruising on other areas of your body that are accompanied by other symptoms, such as easy or excessive bleeding.

Other potential causes of bruising on legs

It’s also important to note another possible cause of unexplained leg bruising in a child, loved one, or friend is abuse. This can include things like domestic abuse, child abuse, and elder abuse. Contact your local authorities or an abuse hotline if you suspect someone is being abused.

If you or your child has unexplained bruising, it may be time to see your doctor.

See your doctor if you notice the following:
  • large bruises that occur frequently and for no apparent reason
  • bruises that show no sign of improvement after a week or two
  • bruises that appear after starting a new medication or supplement
  • bruises that keep occurring in the same area
  • bruising that’s severe after a minor bump or injury

To diagnose unexplained bruising in you or your child, your doctor will:

  • conduct a physical exam to evaluate the bruises and any other symptoms
  • take your medical history and ask about any medications or supplements as well as a family history of easy bleeding or bruising
  • perform various blood tests, if needed

Your doctor can use blood test results to assess:

  • the levels of certain chemicals substances in your blood
  • organ function
  • blood count
  • blood clotting

In some cases, your doctor may take a sample of bone marrow to test if they suspect you may have a type of cancer based on the results of blood testing.

Treating unexplained bruising on your legs may involve treating an underlying condition. Be sure to follow your doctor’s instructions regarding treatment.

If a medication or supplement is causing the bruising, your doctor may have you stop taking it or prescribe an alternative, if possible.

For vitamin deficiencies, treatment may involve replacing that vitamin through diet or injection.

In some cases, blood or platelet transfusions may help introduce healthy clotting elements back into your blood.

Once a bruise has formed, there’s not a lot you can do to treat it. Applying ice and elevating your leg may help. Bruises will eventually disappear, often changing colors during the healing process.

If you want to prevent bruising, particularly if you bruise easily, be sure to follow these tips to avoid injury to your legs:

  • Contain household clutter and trip hazards, such as electrical cords, particularly on and around stairs.
  • Keep furniture out of areas where you walk so you’re less likely to bump into it.
  • Make sure your house is lit well so you can see where you’re walking and what’s around you or on the floor.

Many things can cause you or your child to have unexplained bruises on your legs. You most likely just bruise more easily than others, and therefore don’t remember the injury or bump that caused the bruise.

In other cases, bruising can result from a medication, supplement, or underlying health condition. If you find that you or your child’s bruises occur frequently, are large, and don’t improve after a week or two, see your doctor.