Bruises appear naturally red/purple then turn eventually yellow/green.

Cause

• Occurs when you hit against something (injury).
• Normal process of ageing  (skin become thinner)
• Where capillaries (a delicate-small vein like tube which carries blood to different parts of the body) bursts, collides or has been broken by hitting the skin leaking blood for example:

Skin conditions

For example:

• Purpura
• Petechiae (small dots 2mm in diameter, occurs generally if sensitive to medication)
• Telangiectasias

Medication

For example:

• Taking medication that affects your blood vessels i.e. Antiplatelet or anticoagulant medication
• Non steroidal anti-inflammatory medication i.e. Aspirin,  ibuprofen or a medication that is one sensitive to (weakens one immune system)
• Corticosteroids
• Taking medication that affects your blood counts i.e. platelets, neutrophils
• Chemotherapy side effects
• Radiation side effects