Any sunburn is serious to an extent, in the sense that they increase one’s risk of developing skin cancer. However, some sunburns are more immediately serious than others. With that in mind, some signs that your sunburn is severe or is a symptom of a serious illness or infection include the following: • Blisters on the face, genitals, or hands • Burn covers a large area • Large or severe blisters • Severe pain, swelling, or tenderness • Symptoms of heat exhaustion or heat stroke, such as confusion, dehydration, dizziness, fainting, heart palpitations, peculiar lack of sweat, rapid breathing, slurred speech, and unconsciousness • Symptoms of infection, including chills, fever, pus, or red streaks that run away from an open blister