Bruises are bluish or purple-coloured patches that appear on the skin when tiny blood vessels called capillaries break or burst underneath.
The blood from the capillaries leaks into the soft tissue under your skin, causing the discolouration. Over time, this fades through shades of yellow or green – usually after around two weeks.
Bruises often feel tender or swollen at first.
What about dark skin and bruising?
You can still bruise if you've got dark skin, but they may show up more on fair skin.
What causes bruising?
Bruising is caused by internal bleeding under the skin, and occurs when a person has injured themselves.
Some people are naturally more likely to bruise than others – for example, elderly people may bruise more easily because their skin is thinner and the tissue underneath is more fragile.
How can I reduce bruising?
Treat bruises on your skin by limiting the bleeding. You can do this by cooling the area with a cold compress (a flannel or cloth soaked in cold water) or an ice pack wrapped in a towel.
To make an ice pack, place ice cubes or a packet of frozen vegetables in a plastic bag and wrap them in a towel. Hold this over the area for at least 10 minutes. Do not put the ice pack straight on to your skin as this will be too cold and could hurt.
Over-the-counter painkillers such as paracetamol or ibuprofen may help relieve the pain associated with bruising.
When to see a doctor
Most bruises will disappear after around two weeks. If the bruise is still there after two weeks, see a doctor.
You should also see a doctor if you suddenly get lots of bruises or start to bruise for no obvious reason. Unusual bruising is sometimes a symptom of an underlying illness, such as a problem with the way your blood clots.
Bruises don't just happen under the skin – they can also happen deeper in your tissues, organs and bones. While the bleeding isn't visible, the bruises can cause swelling and pain.
If you're worried that you may have internal bruising from an injury or accident, visit the nearest accident and emergency (A&E) department.