Differential Diagnosis for Blister Rash from Bug Bite

• Single most likely diagnosis
  • Insect bite reaction (e.g., mosquito, flea, or bed bug bites): This is the most common cause of a blister rash from a bug bite, often presenting with localized itching, redness, and blistering at the bite site.
• Other Likely diagnoses
  • Contact dermatitis: This can occur if the individual has an allergic reaction to substances on the bug's body or saliva, leading to a blistering rash.
  • Scabies: Caused by the mite Sarcoptes scabiei, scabies can present with severe itching and blistering rash, especially in areas like the fingers, wrists, and groin.
  • Chigger bites: Chiggers can cause intense itching and blistering, particularly in warm, moist areas of the body.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Rocky Mountain spotted fever (RMSF): Although rare, RMSF is a potentially life-threatening disease transmitted by ticks, characterized by fever, headache, and a distinctive rash that can blister.
  • Lyme disease: Another tick-borne illness, Lyme disease can cause a range of symptoms including a characteristic "bull's-eye" rash, which may blister in some cases.
• Rare diagnoses
  • Blister beetle dermatitis: Certain species of blister beetles can cause a blistering rash upon contact with their bodily secretions.
  • Tungiasis: Caused by the sand flea Tunga penetrans, tungiasis can lead to a blistering rash, especially on the feet.
  • Leishmaniasis: Spread by the bite of an infected sand fly, leishmaniasis can cause skin lesions that may blister, among other systemic symptoms.