Phlebitis literally means 'inflammation of a vein'.
The vein becomes inflamed because there is blood clotting inside it or the vein walls are damaged.
Superficial thrombophlebitis is the term for an inflamed vein near the surface of the skin (usually a varicose vein), caused by a blood clot.
Superficial thrombophlebitis results in painful, hard lumps underneath the skin and redness of the overlying skin.
This is usually on the lower leg, although it can occasionally affect surface veins in the arms, penis or breast.
Superficial thrombophlebitis is typically more annoying than serious.
Usually, the blood clot clears and the inflammation dies down within a few weeks.
Most people with superficial thrombophlebitis are otherwise well. There shouldn't be any foul discharge or abscess, and it's normally just lumps under the skin rather than swelling of the whole calf. This may be painful, but it shouldn't prevent you walking reasonably well.
You're more at risk of superficial thrombophlebitis if you:
Phlebitis is inflammation, not infection, so antibiotics aren't helpful.
You can follow this advice to help reduce any pain and swelling:
rub an anti-inflammatory cream or gel on the area if the affected area is only small
When the inflammation settles, you may be left with darkened skin and the lump may take three or four months to go. But most people make a full recovery.
If the thrombophlebitis occurred in a varicose vein, it is likely that the varicose veins will keep coming back, possibly with further episodes of thrombophlebitis. This is because there's a basic problem with the vein, and you may need this removing. Read about the treatment of varicose veins.
There's a small chance of the blood clot travelling along the vein to where it meets a deeper vein, and a DVT developing.
This is more likely if the surface clot extends into the upper thigh or groin, or behind the knee (in places where superficial veins meet deeper veins).
It is also more likely to occur if the affected vein is a normal vein, rather than a varicose vein, if you have had a DVT before, or if you are immobile.
A DVT can cause pain, swelling and a heavy ache in your leg – see your GP immediately if you experience these symptoms.
Read more about DVTs.