Bite Prevention for Runners and Cyclists: How to Train Without Getting Bitten

Trail runner on a narrow woodland path at golden hour, tall summer grass along the trail and mist over a meadow beyond the trees

TL;DR — key takeaways

  • Exercise makes you an easier target: you breathe out far more carbon dioxide, run hotter and sweat more — the three signals mosquitoes and horseflies track best.
  • Sweat also shortens how long repellent stays on your skin, so timing and reapplication matter more than for a casual walk.
  • Apply a PMD-based repellent to exposed skin 10–15 minutes before you start, and reapply on longer sessions as the label directs.
  • For trail runners and gravel riders, ticks — not mosquitoes — are usually the bigger risk. Check ankles, waistband and hairline after every session.
  • Dusk and dawn sessions near water, woodland or long grass are the highest-risk windows across Central and Northern Europe.

Anyone who trains outdoors has had the same evening: a perfect run along the river, and a forearm covered in bites by the time you stretch. That is not bad luck. Endurance exercise amplifies almost every signal biting insects use to find a host, and it simultaneously makes insect repellent wear off faster. Here is what actually works for runners and cyclists — before, during and after the session.

Why runners and cyclists get bitten more

Mosquitoes find people by following a plume of exhaled carbon dioxide, then homing in on body heat and skin odour at close range. Every one of those cues goes up when you train:

  • Carbon dioxide. Breathing rises several-fold during moderate to hard effort, so your CO₂ plume is far larger than at rest and reaches further downwind.
  • Body heat. Working muscles raise skin temperature, and mosquitoes use heat to make the final landing decision.
  • Skin odour. Sweat brings lactic acid, ammonia and other compounds to the surface — the chemistry that makes some people more attractive to mosquitoes than others.

Horseflies and blackflies work differently again: they are strong fliers that are drawn to large, dark, warm, moving objects, which describes a cyclist almost perfectly.

Speed protects you — until you stop

Mosquitoes are weak fliers and struggle to land on someone moving at pace. That is why most bites on a ride happen at traffic lights, on slow climbs, at the café stop, or in the ten minutes after you finish, when you are hot, still sweating and no longer moving. Horseflies do not give you that grace period: they will follow a moving bike, particularly on warm, still afternoons near rivers, lakes and livestock.

Where and when you are most exposed

Session type Main biter Peak risk What actually helps
Evening road run near a park, river or lake Mosquitoes Dusk and dawn, warm humid days Repellent on arms, neck and ankles before you leave
Road cycling on lowland routes Horseflies, blackflies Warm, still afternoons, June–August Cover shoulders and thighs; repellent on exposed skin
Trail running in woodland or long grass Ticks, mosquitoes, harvest mites Spring to autumn, all day Repellent on lower legs; full tick check afterwards
Gravel and mountain biking Ticks, horseflies May–September Longer socks, repellent, post-ride skin check
Alpine or upland sessions Midges, blackflies Still, damp mornings and evenings Cap plus repellent around hairline and neck

Making repellent work under sweat

The commonest mistake is treating repellent like sunscreen you apply once and forget. Sweat, friction from clothing and water bottles all remove it. A simple routine that survives a training session:

  1. Apply to cool, dry skin 10–15 minutes before you start, not while you are already warming up and damp.
  2. Sunscreen first, then repellent. Let the sun cream absorb for a few minutes, then apply repellent over the top.
  3. Never spray towards your face. Spray into your hands and wipe onto the neck, ears and hairline, avoiding eyes and lips.
  4. Cover the forgotten zones: ankles above the sock line, the back of the calves, the gap between glove and sleeve, and the neck under a helmet strap.
  5. Reapply on long efforts. Heavy sweating, rain and a mid-session swim all cut protection time short — follow the product label, and see our guide to how long insect repellent lasts and when to reapply.
  6. Wash your hands before eating gels or bars, exactly as you would after sun cream.

Kit choices that reduce bites

Clothing does a lot of the work, and it costs you nothing on race day:

  • Light-coloured jerseys and vests are less attractive to horseflies than black kit.
  • Mosquitoes can bite through thin, stretched lycra, so tights are not a substitute for repellent on the skin underneath.
  • Longer socks or calf sleeves are the single best defence for trail runners against ticks and harvest mites.
  • A cap or a helmet liner keeps midges out of your hair on still upland mornings.
  • If you train in the same river-valley or forest routes all summer, plan around the biters the way you would around weather — the same logic we use in our guide to the best insect repellent for hiking and trekking.

Ticks: the risk runners underestimate

Ticks do not fly or jump. They wait on grass and low vegetation at roughly ankle-to-knee height and grab onto whatever brushes past — which is precisely what a trail runner or gravel cyclist does for two hours. In much of Europe the common castor bean tick, Ixodes ricinus, can carry the bacteria that cause Lyme borreliosis, and in parts of Central Europe the tick-borne encephalitis (TBE) virus.

Because ticks usually need time attached to transmit Lyme bacteria, a prompt check after every session is genuinely protective:

  • Shower and check within a couple of hours of finishing.
  • Look at ankles, behind the knees, the back of the thighs, the groin, the waistband line, armpits, and the hairline.
  • Remove any attached tick straight away with fine-tipped tweezers, gripping as close to the skin as possible and pulling steadily upwards. No oil, no heat, no twisting.
  • Note the date. If a spreading circular rash or flu-like symptoms appear in the following weeks, tell your doctor when and where you were bitten.

After the session

Cool down, shower and treat the bites you did get. Cooling a fresh bite reduces the itch, and not scratching is what keeps it from becoming infected — a real consideration when a saddle strap or sock rubs over the same spot on tomorrow’s ride. Seek medical advice for a rapidly spreading red, hot, painful area, for a bite that worsens after a few days, or for any breathing difficulty or widespread rash after a sting.

How incognito® helps

Our Insect Repellent Spray 100ml is built on PMD (Citrepel®), a plant-derived active from Javanese citronella, Cymbopogon winterianus. PMD is the same class of active that public health bodies list alongside DEET for skin-applied protection, it is clinically proven, vegan and biodegradable, and it is recommended against both mosquitoes and ticks — the two that matter most to anyone training outdoors.

Being DEET-free has a practical upside for athletes as well: DEET is a solvent known to damage some plastics and synthetic materials, which is a real nuisance around sunglasses, bike computers, watch straps and technical fabrics. And for the bites that slip through, Zap-Ease is a small, pocketable way to take the itch out of one before it turns into three days of scratching.

FAQs

Do mosquitoes really bite you more when you exercise?
Yes. Exercise increases exhaled carbon dioxide, skin temperature and sweat compounds such as lactic acid — the main cues mosquitoes use to locate and land on a host.

Does sweat wash off insect repellent?
It shortens how long it works. Heavy sweating, rain and towelling all remove repellent from the skin, so long sessions need reapplication according to the product label.

Should I apply sunscreen or repellent first when cycling?
Sunscreen first. Let it absorb for a few minutes, then apply insect repellent on top of the exposed skin.

Can mosquitoes bite through running tights or cycling shorts?
They can bite through thin, stretched synthetic fabric. Looser layers help, but repellent on the skin remains the reliable protection.

Do I need repellent for a short 30-minute run?
At dusk near water, woodland or long grass, yes — most bites on short runs happen in the cool-down, when you have stopped moving but are still hot and sweating.

How soon should I check for ticks after a trail run?
The same day, ideally within a couple of hours. Prompt removal lowers the risk of Lyme transmission, which generally requires the tick to stay attached for a prolonged period.

Sources

This article is general information, not medical advice. Always follow the product label for application and age guidance, and speak to a doctor or pharmacist about symptoms after a bite or sting.