Deer Fly Bite: Is It Poisonous? Uncovering the Truth

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Deer flies are small, blood-sucking insects known for their painful bites. These flies have razor-sharp “lips” that slice open the skin to feed on the resulting blood pool, making them a nuisance for humans and animals alike MIT Medical.

While a deer fly bite can be painful and cause discomfort, it is not generally poisonous. However, there can be instances of localized infections or allergic reactions for some individuals. It’s essential to clean the bite wound and monitor it for signs of infection or severe swelling NC State Extension Publications.

Remember that deer flies are more of a nuisance than a significant threat. Nevertheless, it’s crucial to take precautions such as wearing protective clothing and using insect repellent to prevent bites while spending time outdoors, especially in areas where deer flies are known to be prevalent.

Understanding Deer Fly Bites

Deer Flies: An Overview

Deer flies are insects known for their painful bites. They are typically found in or near wooded areas, and they feed on the blood of mammals, including humans.

Deer Fly Bites: Symptoms and Effects

Deer fly bites can cause a range of symptoms, including:

  • Pain
  • Swelling
  • Redness
  • Itchiness

These insects use their razor-sharp “lips” to slice the skin, creating a pool of blood to feed on. The saliva they inject into the wound can cause an allergic reaction in some individuals, leading to severe swelling and other more serious complications.

Keep in mind that deer fly bites are not poisonous, so most people will only experience mild symptoms.

In a comparison between deer flies and other common biting insects, here are the main differences:

Insect Bite Type Pain Level Poisonous
Deer Fly Sharp “lips” slice skin Painful No
Mosquito Needle-like proboscis Mild No
Bee Stinger Painful Yes (for some people)

It is essential to treat deer fly bites promptly to avoid infection and reduce discomfort. Wash the bite area with soap and water, and take an antihistamine or apply creams to reduce itching if necessary.

Is a Deer Fly Bite Poisonous?

Infection and Diseases Associated with Deer Fly Bites

Deer fly bites are not considered poisonous but can be painful and lead to infections or diseases. Deer flies have razor-sharp “lips” that slice the skin open, allowing them to feed on the blood pool created by the bite 1. The bite can cause itching for days, and if scratched, may lead to an infection 2. Here are some possible complications:

  • Tularemia: Deer flies are capable of transmitting tularemia, a bacterial disease, to humans. This disease may cause fever, chills, and swollen lymph nodes 3.
  • Infection: Scratching the itchy bite may break the skin, leading to secondary bacterial infections.

Symptoms and Comparison

Deer fly bites tend to occur around the head and neck areas and result in different symptoms depending on the individual. It is important to monitor the bite and seek medical attention if necessary. Here is a comparison of common symptoms:

Symptom Severity Example
Itching Mild Slight itch at the site of the bite
Swelling Moderate Swollen area around the bite, sometimes red and warm to the touch
Fever Severe High body temperature, indicates a possible infection or disease

Tips to Reduce Deer Fly Bite Risks

There are some precautions that can be taken to minimize the risk of deer fly bites and associated complications:

  • Wear protective clothing, such as long sleeves, pants, and a hat.
  • Apply insect repellent containing DEET or Picaridin to exposed skin.
  • Avoid areas near ponds, streams, marshes, and lakes, where deer flies are more common4.

Recognizing and Treating Deer Fly Bites

Immediate Care After a Bite

Deer fly bites can be painful, but they are not poisonous. If you’re bitten by a deer fly, here are some immediate care steps:

  1. Clean the bite area: Gently wash the bite with soap and water to reduce the risk of infection.
  2. Apply a cold compress: To minimize pain and inflammation, place a cool compress or ice pack wrapped in a cloth on the bite site for 15-20 minutes.

Remember, you should always:

  • Avoid scratching the bite, as this can worsen the inflammation and increase the risk of infection.

When to Seek Medical Treatment

Although deer fly bites aren’t poisonous, in rare cases, they can lead to severe reactions or infections. Seek medical treatment if you experience any of the following symptoms after a bite:

  • Trouble breathing or shortness of breath, as this may indicate a severe allergic reaction
  • Hives, nausea, or vomiting also suggest a severe reaction to the bite
  • Signs of infection, like increasing redness, warmth, or swelling at the bite site

In some cases, your doctor may prescribe antibiotics to treat or prevent an infection resulting from a deer fly bite.

Remember, it’s essential to monitor your symptoms and take action if your condition worsens. Deer fly bites are generally harmless, but it’s always better to be cautious and seek professional medical advice when necessary.

Preventing Deer Fly Bites

Personal Protective Measures

Deer fly bites can be painful, and while they are not poisonous, they can cause itchiness, swelling, and mild redness. To protect yourself from deer flies, consider wearing a hat with an attached veil or mesh netting, covering your skin with light-colored clothing, and tucking pants into socks or boots. Apply insect repellents containing DEET to exposed skin for added protection. Remember:

  • Wear a hat with a veil or mesh netting
  • Cover skin with light-colored clothing
  • Tuck pants into socks or boots
  • Use DEET-based insect repellents

Environmental Control

To reduce deer fly populations in your surroundings, be aware of their breeding habitats, such as wetlands or marshy areas. Limit your time spent near these habitats during deer fly season. Another effective strategy is to use a fan when outdoors, as deer flies are weak fliers and cannot navigate well in strong airflow. Steps to control the environment:

  • Avoid wetlands and marshy areas
  • Limit outdoor activities during deer fly season
  • Use fans to create airflow


Trapping is an effective way to control deer fly populations, especially in larger areas like yards or pastures. Sticky traps can be hung from trees or fences to catch flying adults. Alternatively, use water traps to attract egg-laying female deer flies and prevent them from producing more offspring. Trapping methods:

  • Sticky traps hung from trees or fences
  • Water traps targeting egg-laying females
Method Pros Cons
Personal protection Reduces skin exposure to bites May be uncomfortable in hot weather
Environmental control Reduces overall deer fly presence Requires vigilance and planning
Trapping Effective in large areas Requires periodic maintenance

Other Biting Flies and Insects

Horse Flies and Black Flies

  • Horse flies are large, fast-flying insects with a painful bite
  • Black flies are smaller but also inflict a painful bite

Both of these flies can transmit diseases like rabbit fever. Their bites can cause itching, redness, and swelling.

Biting Midges and Sand Flies

  • Biting midges (also known as “no-see-ums”) are tiny insects with a painful bite
  • Sand flies transmit leishmaniasis, a parasitic disease

Biting midges are more bothersome, while sand flies pose a more serious health risk. It’s important to protect yourself from these biting insects when outdoors.

Comparing biting insects:

Insect Size Painfulness Disease Transmission
Deer Fly Moderate Yes No
Horse Fly Large Yes Yes (rabbit fever)
Black Fly Small Yes Yes (rabbit fever)
Biting Midge Tiny Yes No
Sand Fly Small Moderate Yes (leishmaniasis)
  • All these insects are attracted to carbon dioxide, heat, and movement.
  • Bites can cause itchiness, redness, and swelling, but not all of them transmit diseases.

Tips to avoid bites from these insects:

  • Use insect repellent
  • Wear long sleeves and pants outdoors
  • Avoid areas with high insect populations

Remember, it’s essential to take preventive measures to protect yourself from these annoying and potentially harmful bites.






Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Deer Flies from Uruguay


Subject: Biting fly
Location: Northern Uruguay
March 30, 2016 11:30 am
Hello. These are driving me crazy. and I finally got some pictures of them. The are pretty aggressive, circle around, then land on a leg and start biting. They produce painful swollen welts. They have been around from early summer through the fall. They appear to be territorial, yet they “hunt me” in pairs.
Any identification would be appreciated.
Signature: Louis

Deer Fly
Deer Fly
Deer Fly
Deer Fly

Dear Louis,
Some of our more sensitive readers might want us to tag your submission as Unnecessary Carnage, but in our minds, blood suckers are fair game when it comes to battling with insects.  Interestingly only female Mosquitoes and Horse Flies flies suck blood, and the same holds for your Deer Flies in the Subfamily Chrysopsinae, relatives of Horse Flies in the family Tabanidae, like your individuals.  Males and females both feed on nectar, but females need blood before they are able to produce eggs.  Were you painting?  Was it oil or resin based paint?  We understand that some Beetles are attracted to fumes from paints and other solvents, but we don’t know if some Flies are similarly attracted.  You can get more information on Deer Flies on the Orkin site.

Four Deer Flies
Four Deer Flies

Letter 2 – Chartreuse Fly Acts Like Deer Fly?


Help! We have recently discovered these large bright green insects which look like flies all over our 2 pet pigs. We have seen them twice & only around dusk. We have recently moved to a 46 acre farm in rural North Central Florida & the pigs are in an area that is mostly woods. They appear to be biting flies & sound a little buzzy. They act like deer flies & do not return to the pigs (on that day, at least) when they are sprayed with a pyrethrin insect repellant. I have not engaged in mortal combat with one so I have no photo yet. I’d love to identify them before we move our goats & horses here. Any help in identifying them would be appreciated. Thanks in advance,

Hi Sandra, We would love to get that photo when you go to war. We are thinking you might have Sweat Bees, which are often a brilliant green color. they are attracted to sweat, hence the name. Bees have four wings while flies only have two wings, should you ever get close enough to notice.

Thanks for the prompt response, but I think that they must be something different for three reasons: 1) I looked up some photos of sweat bees online & they didn’t look like that. 2) I was on stakeout at dusk today, but none showed up. I was visited by 2 deer flies & the ones I’m trying to identify are at least 2 – 3 times the size of a deer fly & sweat bees are supposed to be pretty small. 3) Pigs don’t sweat. (Technically they do sweat on their noses, but these guys were not near their heads, they were on their sides like a deer or horse fly would be.) Will keep on the lookout & capture dead or alive for future photo ID. Thanks again, Sandra

Here are the photos of the fly I grabbed off the pig tonight. I froze it before photographing.

Hi Sandra,
I wanted to reply to you quickly so that you would know I was working on your question. You have some type of Horse Fly, Family Tabanidae, which also includes Deer Flies. I have found references on the internet to Green Horse Flies being troublesome in Maine, and also to their proliferation in hot weather at the St. Elizabeth’s Medical Center in Kentucky, but no species name or photos. I have a query out to the Museum of Natural History in Los Angeles and hope to hear back soon. Female Horse Flies are the blood suckers while males feed on nectar and pollen. The larvae are usually aquatic.

Letter 3 – Deer Fly


I am from Atlantic Canada and this summer I went camping with a friend and this little fly wouldn’t leave me alone. It wasn’t interested in my blood because the few times it landed on me it just stayed there and didn’t move. I was able to get tis picture of it and noticed the odd coloration in its eyes. You have any ideas?
Janita Sullivan

Hi Janita,
Your photo is so pretty. We don’t recognize the species of fly. We haven’t pestered Eric Eaton for an identification in a bit, so we will contact him. Here is Eric’s response: “Hi, Daniel: Neat images! The fly is one of the deer flies in the genus Chrysops (family Tabanidae, which includes the horse flies). Personally, I think the psychedelic eyes are a way of mezmerizing their victims (they slice and dice, then lap up the blood that flows from the wound). Deer flies tend to go for the head of human victims, so simply wearing a hat will help discourage them. Keep up the great work! Eric”

Letter 4 – Deer Fly


Deer Fly has crazy eyes!
Location:  Fairfield, Maine USA
August 13, 2010 3:47 pm
Dear Bugman,
I got a close up of a Deer Fly resting on a plant. I never had looked at one for long enough to see their strikingly colored eyes. Usually whenever I see them they are bombarding my head! I wonder why this one was not attacking? Do they only go for mammal at certain times of their life?
Thank you,
James R

Deer Fly

Hi Again James,
We are ignoring some of our other submissions to post so many of your lovely photos, but it is also true that Deer Flies are not well represented on our site.  We believe your Deer Fly is in the genus Chrysops.  It is amusing that BugGuide posts instructions for 4 specific views that should be taken of each individual Deer Fly to ensure correct identification.  Can you call the fly back to take some additional photos?

Thanks Daniel!
Unfortunately I have had no luck calling the fly back for another shoot.  I will get more if I ever see
one again that is not attacking me.
Best wishes,


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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1 Comment. Leave new

  • Have to agree with your sympathetic response. When we lived in northern BC Canada there were biting flies and other insects that were impossible to ignore… large, painful bites. We used to say they flew in with knife and fork and cut off a chunk and packed it away. Especially unwelcome when young children are involved.


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