Insect Bite Differential Cheatsheet
Key Concept: Bedbugs = LINEAR pattern, central punctum, exposed skin, found in furniture. Scabies = burrows, finger webs, nocturnal itch, household contacts. Lice = nits on hair. Chiggers = ankle/waistband, outdoor exposure.
| Diagnosis | Key Features |
|---|
| Bed Bugs |
- Linear pattern of 3 papules ('breakfast, lunch, dinner')
- Central hemorrhagic punctum; found on exposed skin (arms, neck)
- Household contacts affected; found webs/bugs in furniture
- Treatment: treat environment (heat/pesticide); oral antihistamine for itch
|
| Scabies |
- Intensely pruritic; worse at night (nocturnal pruritus)
- Burrows in finger webs, wrists, waistband; spares head in adults
- Household contacts simultaneously affected; mites on skin scraping
- Treatment: permethrin 5% cream (all household members)
|
| Pediculosis (Lice) |
- Nits (eggs) attached to hair shafts; lice visible on scalp/seams of clothing
- Head lice: posterior scalp/neck; body lice: clothing seams; pubic lice: genital area
- Treatment: permethrin 1% or pyrethrin (head lice)
|
| Chiggers |
- Papules at ankle/waist (areas where clothing is tight); extremely pruritic
- Outdoor exposure (tall grass, forest); larvae inject digestive enzymes
- No human-to-human transmission; treatment: symptomatic only
|