Horsefly bites vs deer fly bites
Where on the body. Horseflies go for legs, back and shoulders and leave a larger, often bleeding wound. Deer flies circle the head and bite the scalp, neck and shoulders. Both bite in daylight near water, and both hurt at the moment of the bite.
Side by side
| Horsefly bite | Deer fly bite | |
|---|---|---|
| Looks like | a large raised red weal, often with a visible cut and a spot of bleeding | a painful red weal, smaller than a horsefly bite |
| Pattern | single, occasionally two | single or a few, often on the scalp and neck |
| Size | 10–60 mm | 5–30 mm |
| Appears | immediate, sharp — you feel this one | immediate sharp pain |
| Lasts | several days; slower to heal than most bites | a few days |
| Itch | ●●●○○ 3/5 | ●●●●○ 4/5 |
| Pain | ●●●●● 5/5 | ●●●●○ 4/5 |
| Usually on | legs, back, shoulders — often through thin clothing | scalp, neck, shoulders — they target the highest point of a moving person |
| Active | hot, still, sunny days; they hunt by sight | daylight hours, worst in humid weather near water |
| Where from | near water, livestock, and open sunny ground — lakesides and pasture in particular | wetlands, lakesides, wooded trails |
| Disease risk | none known in the US | tularemia (rare) |
What actually settles it
Height again. Deer flies target the highest point of a moving person; horseflies work lower.
Wound size. Horsefly mouthparts cut like scissors — larger wound, more bleeding, slower healing and a higher chance of infection. Keep it clean and covered.
The insect. Deer flies are smaller with patterned wings and gold-green eyes; horseflies are big, dark and heavy.
Repellent barely works on either. Shade, light clothing and moving away from water on hot still days do more.
When either one needs a doctor
- spreading redness and warmth over days — these bites become infected more often than most
- fever
- dizziness or widespread rash
- spreading redness and warmth
- fever with swollen glands after a bite
Questions
Can you have both at once?
Yes, and it happens more often than people expect — which is why the pattern of the bites matters more than any single mark.
Which one is more serious?
Deer fly bite carries the wider disease risk in the US. For both, the common complication is infection from scratching.
What if I still cannot tell?
Photograph the bites over several days and note where on your body they appear and when. Progression and position identify a bite far more reliably than a single photograph.
Get a photo assessment in the app
Everything above is free to read. The app adds what a page cannot: point your camera at the bite and get an assessment of the most likely cause, a severity read, and a day-by-day care plan — including the specific signs that mean you should be seen.
iPhone and iPad. Free to download.