A broken blood vessel under the skin is what causes a thumb to bruise. Treating a bruised thumb begins with reducing the swelling using ice and elevating the thumb above the heart. Symptoms of pain will usually occur, requiring ingestion of a pain killer for relief. After the first 48 hours, applying heat to the bruised area will help aid the healing process, and the bruise usually will disappear after a couple of weeks. In some cases, however, consultation with a doctor is required, particularly in case of acute pain that persists or if the person is on blood thinning medication.
Soft tissue surrounds the bone on the thumb, and this tissue has many blood vessels running through it. Sudden trauma to the area can cause one or more of those blood vessels to break. Blood leaks out into the tissue and pools there, causing the bruised thumb. The bruise becomes visible on the surface as a reddish color at first, then turning purple in color within a day or two. Over the course of a few weeks the bruise will fade to yellow and disappear once the body breaks down the blood cells and eliminates them.
Most bruises to the thumb will heal over time if left unattended. Treating the bruised thumb, however, can speed up the healing process. Applying ice immediately after the bruise appears and then periodically every couple of hours for about 15 minutes at a time will reduce both the swelling and the bruising. This can be accomplished by wrapping the ice in a towel before applying it and by keeping the thumb elevated above the heart to help keep blood from pooling excessively. Reducing the effects of pain by taking a non-aspirin painkiller is recommended as well. Aspirin products will thin the blood and usually causes prolonged bleeding.
Following the ice treatment over a period of one or two days, either a heat pack or wrap should be used on the bruised thumb in a warm wash cloth several times daily. Doing so will help the thumb heal faster. Thereafter, the pain should subside within a week, and the bruise should heal entirely in about two-weeks. If acute pain persists, however, the injured person will need to seek medical attention as this may signify a sprain or even a broken thumb. Accurate diagnosis might then involve x-rays to check the bones in the thumb, in addition to an examination and treatment by a medical doctor.