Home . News . Where to donate . What happens . Who can donate . How to enrol . All about blood . About the NBS . How to help . Contact the NBS . Site map . Fun zone  Occasional bruising Donating blood is simple Apheresis donation Donor card scheme FAQs Where your blood goes Your Donation Feeling Faint Occasional Bruising Bone Marrow Donation Occasional bruising In this page we've got the full official explanation as to why some people might be prone to bruising after a donation. And it goes something like this: Although we hope that no donor will have any ill effects from giving blood, occasionally bruises on the arm may develop. This can look very dramatic, especially if it's unexpected. We hope that this page will help to explain why bruising occurs. What is bruising? Bruising is caused by bleeding under the skin. For example, a hard knock which does not break the skin can damage fragile blood vessels which lie just beneath. These damaged blood vessels leak a small amount of blood, which collects in the area as a bruise. With time, the familiar blue-black discolouration changes to yellow and eventually fades and disappears. Why can it happen after blood donation? When the needle is taken out of the arm, bleeding will continue until the small hole in the vein closes up. The way to prevent this is to apply pressure to the arm over the site where the needle was inserted. This must continue until all signs of bleeding have stopped. Failure to maintain this pressure is the most common cause of bruising. Secondly, when the donation needle is put into the arm, damage to the opposite wall of the vein may occur, causing a small hole through which blood can escape. This is not always seen during the donation but may become apparent afterwards. Thirdly, there are tiny fragile blood vessels running just under the skin, as well as the larger veins from which a blood donation is obtained. When the donation needle is inserted into the arm, one of these small vessels may be damaged and bleeding occurs. It is impossible to predict this, as such vessels are not usually visible. What can be done? The single most important way of preventing a bruise is to apply pressure and a suitable dressing to the place where the needle was inserted. The dressing should be kept on for a minimum of 4 hours. If a bruise occurs during the donation the nurse or doctor will assess the situation and may discontinue the donation. This will prevent the bruise from worsening. Additionally, if you are wearing a tight sleeve, we may ask you to remove that article of clothing. A tight sleeve can act as a tourniquet, cause congestion in the vein and promote bruising. What can you do? Bruising may be painful. You should avoid heavy lifting which may aggravate the pain in the arm. However, gentle movement may be beneficial. Bruising can look very ugly, but is usually harmless and will disperse with time. However, if you experience any of the following, you should seek further help:- Severe pain. Numbness or 'pins and needles' in the arm, hand or fingers. Swelling and/or redness of the arm. If any of these occur, or if you are worried, you can obtain advice by ringing our Donor Helpline on 0845 7 711 711. View Current Blood Stocks   Bradley's story Privacy & Legals notice  RETURN TO TOP OF PAGE