allergic reaction

Reaction to Arthropod Bite

Bhagwan Bang, MD
South Alabama Pediatrics, Opp, Alabama

15-year-old male presented with itchy fluid-filled bumps on both legs (Figure, left). He denied fever, trauma, medication use, insect bites or any family history of blistering or autoimmune disorder.

Arthropod bite

Bullous arthropod bite reaction occurs in sensitized individuals as a delayed hypersensitivity immune reaction to insect bites. Patients typically present with grouped localized pruritic or asymptomatic blistering and otherwise appear well. Unless secondarily infected, the blisters are non-erythematous and non-purulent, and develop within hours to days of the bite.

Location of the lesion helps indicate a causative arthropod bite. Bites on the forearm, thigh and lower abdomen are typically caused by mites. Flea bites are usually located in lower extremities (which I suspected in this case). Bed bug bites (Figure, right) are found on the entire body and tend to occur in groups of 3 (so-called breakfast, lunch, and dinner). 

This can be differentiated, from contact dermatitis, which tends to occur in streaks or linear fashion and also can be painful and pruritic. Fungal infections generally occur on the palm or sole. Absence of drug use will help in ruling out drug-induced pemphigoid, whereas bollous scabies typically involve moist areas of the body. 

Patient was suggested to use vinegar water soaks or aluminum acetate compresses (Domeboro), topical mupirocin (Bactroban), and oral antibiotics if the condition did not improve.


  1. Lane K, Lumbang W. Pruritic blisters on legs and feet. J Fam Pract. 2008;57(3):177-179.