Nosebleeds are more often annoying than a serious health threat, although they can indicate the presence of other underlying illnesses.

Most nosebleeds can be treated at home. They are messy and can be embarrassing, but most do not need professional medical attention.

What are they?

Most nosebleeds start in the lower part of the septum, the semi-rigid wall that separates the two channels of the nose.

It contains blood vessels that can be broken by a blow to the nose or the edge of a sharp fingernail.

With these nosebleeds - known as anterior nosebleeds - bleeding can occur from one side of the nose (epistaxis) or both (epistaxis bilateral).

They can usually be treated easily at home and do not require medical attention.

More rarely, posterior nosebleeds start when bleeding begins high and deep within the nose.

Blood flows down the back of the mouth and throat even when the patient is sitting up or standing.

This more severe type of nosebleed needs immediate medical attention.

What causes them?

Nosebleeds are caused by the rupture of a small blood vessel called a capiliary in the nose.

The most common cause of this is injury - a good bash to the nose will result in bleeding.

The other main cause is dryness of the inside of the nose. A dry climate or heated indoor air irritates and dries out nasal membranes, causing crusts that may itch and then bleed when picked.

Other causes of nosebleeds are colds, high altitude, allergies and medications.

Nosebleeds can also result from a calcium deficiency.

Occasionally, nosebleeds may indicate other disorders such as bleeding disorders, cancer, high blood pressure or disease of the arteries.

They can also indicate hereditary haemorrhagic telangiectasia, also known as Osler-Weber-Rendu syndrome.

This is a disorder involving a vascular growth similar to a birthmark in the back of the nose.

What is the treatment?

Doctors advise people with lower-septum nosebleeds to sit up straight and pinch the nostrils together firmly for 10 minutes.

An ice pack can also be applied to the nose and cheeks.

The pressure should then be relieved to see if the nose is still bleeding.

If it is, patients are advised to pinch the nostrils for another 10 minutes.

If the nosebleed was caused by atmospheric dryness, the patient should breathe steamy air. After bleeding stops, petroleum jelly can be applied just inside the nose to prevent further bleeding.

Once bleeding has stopped, the sufferer should avoid any strenuous activity for 12 hours. Nor should they blow their nose, as this may dislodge blood clots and cause bleeding to start again.

If bleeding does not stop after 30 minutes of direct pressure, patients should see a doctor.

If blood runs down the back of the throat when pressure is applied to the nose, it could be a higher-septum nosebleed and require a visit to the doctor.

Patients should also seek professional help if nosebleeds occur more than once a week.

What is the treatment for serious nosebleeds?

Cauterisation is the minor surgical procedure used to stop heavy nosebleeds.

It involves destroying tissue with an electric current, a hot iron, or caustic chemicals.

This seals the ruptured blood vessel and prevents further bleeding.