Erythema multiforme refers to a severe reaction to an infection or medicine. It sometimes appears as a rash with blisters at the centre, and can occur on the arms, hands, legs and feet, as well as inside the mouth and on the lips. Because the condition can be triggered by certain medications, Dr Patterson may start by recommending you stop taking any medicine that may be causing the reaction. He may also prescribe an anaesthetic mouthwash to alleviate any discomfort in the mouth. In some cases, antibiotics may be required and steroid tablets may be prescribed in order to control inflammation.