Blisters can sometimes develop from an illness or a toxic reaction. Symptoms of a serious illness can include:

• Shaking chills or fever.
• Muscle or joint aches.
• A moderate to severe headache.
• A vague sense of illness (malaise).
• Abdominal cramping.
• Nausea or vomiting.
• Diarrhea.

Blisters may appear with a viral infection, such as chickenpox or shingles, or after a bite from a poisonous spider, such as a brown recluse, or following a tick bite. Blisters may also occur as a symptom of a toxic reaction to a medication. This reaction is called Stevens-Johnson syndrome.

Your blister or blisters may not be related to another illness. You may have picked up a viral illness, such as the flu, at the same time you got a blister. It could be a coincidence that the blister and signs of illness appeared at the same time.

You have a greater risk of developing an infection and complications from a blister if you also have other conditions, such as diabetes or peripheral arterial disease.

Call your health professional if you have a blister and other signs of illness. A health professional can evaluate your symptoms and recommend treatment.