A black eye is bruising to the tissue under the skin surrounding your eye.
It's usually caused by a blow to the face, such as a punch, or an accident such as a fall.
Sometimes, a black eye can occur after cosmetic surgery to the face, such as a facelift or a nose operation.
The area around the eye turns bluish or purple because tiny blood vessels under the skin burst and blood leaks out into surrounding soft tissue.
Your skin may be painful and swollen and may make it difficult to fully open your eye. Your vision may also be temporarily blurred and you may have a headache.
What to do if you have a black eye
A black eye is not usually serious and you can usually look after it at home if there are no signs of a severe injury (see below).
After a few days, the swelling around your eye will start to go down and the bruise will turn brownish-yellow before eventually fading.
Like any other bruise, a black eye will usually take about a week or two to heal completely.
You can normally help reduce the symptoms of a black eye.
Gently apply an ice pack to the skin around your eye as soon as possible after the injury. You can use a bag of frozen peas wrapped in a tea towel.
The cold will numb the pain and relieve the swelling. During the first day, you should apply the ice pack to your eye for 15-20 minutes an hour every hour.
Painkillers, such as paracetamol or ibuprofen, can be used to help relieve pain. Avoid using aspirin (unless your doctor advises you to take it) because it can make bleeding worse. Children under 16 should never be given aspirin.
See your GP if the pain or swelling is severe or doesn't go away, or the affected area is warm, red or leaking pus (these may be signs of infection).
When to go to A&E
Go to your nearest accident and emergency (A&E) department immediately if:
you have two black eyes (this suggests a type of head injury known as a basilar skull fracture)
you lost consciousness at the time of the blow to your head
you have double vision or loss of vision
you have other symptoms of a severe head injury, such as memory loss, a severe or persistent headache, drowsiness, seizures (fits), or vomiting
you cannot move your eye
you think something has pierced your eye, or there is something stuck in it
your eye is cut or there is blood in your eye
you have other signs of a serious eye injury, such as an irregularly shaped pupil (the black dot at the centre of the eye), pain when exposed to bright light, or flashing lights, spots, halos or shadows in your field of vision
you are taking blood-thinning medication, such as aspirin, or you have a bleeding disorder, such as haemophilia
Any of these situations could mean you have a serious injury and need to be assessed as soon as possible.