Spotting and treating a march fly bite

Dr Hamish Black

Do you know how to spot a march fly? Fret no more, here's a guide on what to look out for and how to treat a march fly bite.

01 March 2023 5 minute read

March flies, sometimes known as horse flies, have earned a reputation as ferocious and persistent biters and a pest to both human and animals.

Up to 3cm in size, you’re most likely to encounter one in the warmer months, especially on clear sunny days without wind. Unfortunately, the beach (along with creeks and estuaries) are their habitats, so they may have spoilt some of your time relaxing on the sand. their habitats, so they may have spoilt some of your time relaxing on the sand.

Most encounters with a march fly will leave you a bit sore, itchy and annoyed, but they are not known to transmit disease.

A march fly bite can prompt an allergic reaction in some people, says Hamish.

“They can cause urticaria, commonly known as hives, where the skin becomes red, itchy and with bumps or welts. The bite can also cause other allergic reactions, including anaphylaxis in severe cases, which can be fatal.” which can be fatal.”

Identifying a march fly bite

March flies are usually easy to spot because they are bigger than normal flies, and there’s also the ouch factor.

“March fly bites hurt a fair bit so you will be aware of the bite as it happens,” Hamish explains. “Whereas mosquito bites are often not noticed [until after the bite].”

How to treat a march fly bite

Hamish suggests treating a march fly bite in much the same way you would a mosquito bite.

“Try not to itch it too much, to avoid skin damage, however, you can try applying ice if pain and swelling is a problem.”

“For kids, it can be a good idea to keep their nails trimmed back so when they do itch, they don’t damage their skin,” Hamish adds.

A non-sedating antihistamine will help to minimise the need to itch. If the bite does become painful, over-the-counter pain medication can help.

When do I need to seek medical treatment?

If your symptoms move beyond general itching, you could be having an allergic reaction.

“You need to get immediate medical attention if you experience significant systemic allergic symptoms, such as swelling around the mouth or difficulty breathing,” Hamish advises.

Ways to avoid march fly bites

There are some steps you can take to avoid march fly bites.

Cover up outside by wearing long clothing. Make sure clothing is not so thin that the flies can bite through it. Be sure to cover your feet too.
March flies have been found to be attracted to dark blue, so avoid that and other dark colours. Research has also found they are less likely to go near stripey clothing because it confuses them.
Apply mosquito repellent evenly to any exposed skin. If you have kids, apply it properly for them. (The most effective repellents contain picaridin, DEET or oil of lemon eucalyptus. Note, natural remedies provide limited protection.)
If you have young children in prams or carriers, drape nets over them.

And if one does land on you, you’ve still got a chance to avoid a bite. March flies take a moment to settle before they bite – so swat them away before they get too comfortable.

Please note: The tips throughout this article serve as broad information and should not replace any advice you have been given by your medical practitioner.

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