Sandflies in New Zealand: What They Are, Where They're Worst, and What Keeps Them Off

The short answer: sandflies are tiny black biting flies found near flowing water and bush all over New Zealand. They're famously bad in Fiordland (including Milford Sound) and on the West Coast of the South Island. According to Health New Zealand, they don't carry disease here, but their bites can itch for days or even weeks. They bite mostly at dawn and dusk. What actually helps is covering up, especially ankles and feet, and using a proper insect repellent. Health NZ names DEET as one of the most effective active ingredients, and Healthify NZ says picaridin and oil of lemon eucalyptus can also be used. On sunny days, put your sunscreen on first and the repellent on top.

What are sandflies in New Zealand?

New Zealand's sandflies are blackflies. Te Ara, the Encyclopedia of New Zealand, notes that their Māori name is namu. Health New Zealand says there are 19 sandfly species in Aotearoa, but only 3 bite people, and only the females bite, because they need blood to produce eggs. At only 2–3 mm long, you'll usually notice the bite before the fly.

Are sandflies dangerous?

No, not in New Zealand. Health NZ is clear: the sandflies here are a nuisance, not a public health risk, and the kinds that bite don't carry infectious diseases. (Overseas sandflies are a different story, which is why some search results look alarming.)

What they do cause is itching, redness and swelling at the bite. Health NZ says these symptoms can last a few days to a few weeks, depending on how you react. One point for anyone arriving from overseas: visitors who haven't been exposed to sandflies before may react more severely than people who live here. So on a first trip from the US, take prevention seriously.

Where are sandflies worst in New Zealand?

Sandflies breed in running water. Health NZ says you'll find many of them near water and humid bush: beaches, lakes, rivers and swamps.

The places with the biggest reputation:

• Fiordland and Milford Sound. Te Ara describes the West Coast and Fiordland as "infamous for their sandflies." The end of the Milford Track, where trampers catch the boat to Milford Sound, is literally called Sandfly Point. Even DOC's leaflet for the short Milford Foreshore Walk says: "Take sandfly repellent with you!"
• The West Coast of the South Island. Te Ara's sandfly nuisance map shows the West Coast standing out as sandfly country, because the region is full of the swift-flowing bush streams they breed in. The same map shows sandflies are seldom a problem on the South Island's drier east coast.
• Abel Tasman. DOC's Abel Tasman Coast Track page notes there are sandflies and recommends carrying insect repellent for them.

They aren't only a South Island thing: Health NZ says the New Zealand blackfly is also found in the North Island. Near a river mouth, bush-lined beach or lake edge, have repellent in the bag.

When are sandflies worst?

Time of day: Health NZ calls them day-biters, mostly biting at dawn and dusk. Te Ara adds the detail: sandflies can't see in the dark, so they seldom bite at night, and they usually stay outdoors.

Weather: Te Ara says sandflies are most active in dull, overcast and humid conditions, when they may bite at a similar rate all day. So a grey, muggy afternoon in Fiordland can be just as bad as sunset.

Season: summer is when most visitors meet them. Searches for "sandflies" in New Zealand climb sharply in December and January (Google Trends, five-year monthly averages). That's also peak holiday season, so pack for sandflies and strong sun together.

What actually keeps sandflies off

Here's what the official advice adds up to:

1. Cover up when you're not moving, particularly ankles and feet (Health NZ). Long pants, socks and closed shoes at dusk help.
2. Use an insect repellent regularly when you're around sandflies. Health NZ says repellents with diethyl toluamide (DEET) or dimethyl phthalate as the active ingredient are most effective. Healthify NZ, the national health information site, says products with 20–25% picaridin or about 30% oil of lemon eucalyptus can also be used, and lists IR3535 among the ingredients that give reasonably long-lasting protection.
3. Get the strength right. Healthify recommends 20–50% DEET for adults and a maximum of 30% DEET for children. Higher strengths last longer, but Healthify says there's no additional benefit above 50% DEET.
4. Reapply when needed. Sweat, swimming and rubbing shorten protection (Healthify); follow the label.
5. For a small sitting area, Health NZ suggests a citronella candle can help put sandflies off. Healthify notes that herbal and essential-oil repellents (citronella, lavender, tea tree and so on) generally have a weaker or shorter-lived effect.

☀️ Sunscreen first, then repellent

• Order: apply sunscreen first, let it dry, then put repellent over the top (Healthify NZ; CDC Yellow Book).
• Why separate products: Healthify says combined sunscreen-and-repellent products are "not generally recommended," because repellent lasts several hours while sunscreen needs reapplying more often. The CDC advises travelers to avoid combination products for the same reason.
• DEET and SPF: the CDC notes limited data showing DEET over sunscreen can lower SPF by about a third, so reapply sunscreen more often.
• The season: Cancer Society NZ's SunSmart advice is to protect yourself outdoors from September to April, especially 10am–4pm, reapplying sunscreen every two hours or after swimming or sweating.

At our place, the SPF 50 lives on a little shelf by the door so nobody forgets it, and I check the UV index on my watch before we head out. If you're travelling somewhere sandfly-prone, keep the repellent right next to the sunscreen as step two.

🧒 Kids and repellent: age limits (Healthify NZ)

• DEET: not recommended under 2 months. Children: max 30% DEET.
• Picaridin: not recommended under 2 years.
• IR3535: not recommended under 6 months.
• Oil of lemon eucalyptus: not recommended under 3 years.
• Children under 10 shouldn't apply their own repellent. Put it on your own hands first, then spread it on their exposed skin, and keep it off their hands.
• Wash it off with soap and water once you're back inside.

Note for American parents: US labels and CDC guidance differ from NZ guidance on some age limits. Healthify's page is written for New Zealand, so it's the one to check while you're here.

Sandfly repellents worth packing from the US

As an Amazon Associate we earn from qualifying purchases.

None of these listings mention NZ sandflies specifically, so we've noted each active ingredient and what NZ health guidance says about it. Read each label before use. Check Amazon for current price.

1. Sawyer Premium Insect Repellent, 20% Picaridin Lotion (4 oz)

A fragrance-free lotion with 20% picaridin, which sits in the 20–25% range Healthify says can be used. A lotion goes onto ankles and necks without spray drifting into eyes. Per Healthify, picaridin isn't recommended for children under 2.

Sawyer 20% Picaridin Lotion on Amazon

2. OFF! Deep Woods Dry Insect Repellent, 25% DEET Spray (4 oz, 2-pack)

An aerosol with 25% DEET. That's within Healthify's 20–50% range for adults and under the 30% maximum for children (not for babies under 2 months). Healthify advises spraying onto your hands first, never straight at a face.

OFF! Deep Woods Dry 25% DEET on Amazon

What about sunscreen-and-repellent combos? You'll see "sunscreen + bug spray" products in the same aisle. We've deliberately left them out of this list. Healthify NZ and the CDC both advise separate products, because sunscreen needs reapplying far more often than repellent does.

Sandfly bites: what to do

Health NZ's advice for sandfly bites:

• Try not to scratch. Broken skin raises the risk of infection.
• Soothe the itch. The most common approach is an antihistamine cream or calamine lotion on the bites. For a severe reaction, an antihistamine pill may be needed. A pharmacist can help you choose.
• Expect it to take a while. Itch, redness and swelling can last a few days to a few weeks.

We've seen that at home. Our daughter Annie gets bubbles from sandfly bites, and they itch for days. They're not the same as mosquito bites, so don't treat them as if they were.

If a reaction seems severe or you're worried, talk to a pharmacist or doctor.

For the day pack, some families like a pocket itch-relief pen:

3. After Bite Advanced Itch Relief Pen (4-pack)

The listing gives the active ingredient as 5% sodium bicarbonate (baking soda), with label directions for adults and children 2 and older. It isn't one of the treatments Health NZ names. Think of it as a portable extra, not a replacement for what Health NZ suggests.

After Bite Itch Relief Pen 4-pack on Amazon

FAQ

How bad are sandflies in New Zealand? In Fiordland and on the West Coast they can be relentless near water at dawn, dusk and on dull, humid days. They don't carry disease here, but bites can itch for days to weeks (Health NZ).

What's the best sandfly repellent in NZ? Check the active ingredient, not the brand. Health NZ names DEET and dimethyl phthalate as most effective; Healthify adds 20–25% picaridin or about 30% oil of lemon eucalyptus. Adults: 20–50% DEET; children: max 30%, with age limits.

Should I put on sunscreen or bug spray first? Sunscreen first. Let it dry, then apply repellent (Healthify NZ, CDC). Reapply sunscreen every two hours, as DEET may reduce its SPF.

Are sandflies bad at Milford Sound? Yes, it's one of the best-known sandfly areas. The Milford Track even ends at Sandfly Point.

What time of day are sandflies worst? Dawn and dusk (Health NZ). They seldom bite in the dark, but on overcast, humid days they can bite all day (Te Ara).

How long do sandfly bites itch? A few days to a few weeks, depending on how you react (Health NZ). Antihistamine cream or calamine lotion is the usual first step.