Bites

Is it a bed bug bite?

How bed bug bites look on the skin, why they show up in lines days later, how they differ from flea and mosquito bites, and when to see a doctor.

The short answer

Bed bug bites are usually small, raised, itchy red bumps, 2–5 mm across, often in a short row or a close group on whatever skin was bare in bed: arms, shoulders, neck and face. They often appear one to several days after the bite, and many people get no reaction at all. On their own they cannot confirm bed bugs, which is why bed bug treatment starts with finding the insect, its droppings or its cast skins.

What bed bug bites look like on the skin

Most bed bug bites are red, raised bumps of 2–5 mm, and DermNet NZ notes a tiny central puncture may be visible. On brown or black skin they can look brown, red or purple and are harder to see, as the NHS points out. A few people react more strongly, with painful swelling or larger welts, which Health New Zealand puts down to sensitivity to the bug's saliva.

The more surprising fact runs the other way: DermNet NZ puts the share of people who show no reaction at all as high as seven in ten. So the person with the bites may not be the only one being bitten, and a clear night is no proof that nothing fed, and why we look for physical evidence before anyone treats.

Lines, clusters and where on the body they appear

The well known pattern is a short line of three, which DermNet NZ notes is sometimes called breakfast, lunch and dinner, made by a bug probing along skin pressed against the mattress. Tight clusters and single bites are just as common. Where they appear follows what was uncovered while you slept, typically the face, neck, arms and shoulders, and sometimes the legs.

Two people in one bed can wake with very different marks, or one with none, because reactions vary so much. Write down where and when each new crop appears; a pattern that only follows nights in one bed is a stronger clue than the marks themselves.

Why bed bug bites show up days later

A bed bug feeds for a few minutes while you sleep and you do not feel it, so the first sign is usually an itchy mark that develops later. The US Centers for Disease Control and Prevention says most people notice bites one to several days afterwards, and in some cases it takes as long as two weeks. Health New Zealand likewise describes bites that may not show for a few days.

That delay is why people blame the wrong night, the wrong bed or the wrong insect. Bites that appear on Wednesday may have come from a hostel bed on Saturday, or from your own bed every night since.

At a glance

Bed bug, flea and mosquito bites compared

Bed bug, flea and mosquito bites compared
Insect	Where on the body	When it shows	Pattern and look
Bed bug	Skin uncovered in bed: face, neck, arms, shoulders	One to several days later, sometimes up to two weeks	Red bumps of 2–5 mm, often in a line or cluster
Flea	Lower legs and ankles, and the waistband	Soon after the bite, day or night	Small groups, intensely itchy, sometimes a tiny central blister
Mosquito	Whatever skin was exposed, indoors or out	Within minutes, then a firmer bump a day or so later	Puffy red bump, usually single or scattered
Carpet beetle larva	Mostly under clothing: thighs, arms, chest	Not a bite; an itchy reaction to the larva's hairs	Itchy bumps with no central puncture

Bed bug, flea or mosquito: telling the bites apart

Flea bites cluster on the lower legs and ankles, and at the waistband, appear soon after the bite and itch intensely, sometimes with a small central blister, as DermNet NZ describes them. Mosquito bites rise as a puffy red bump within minutes on whatever skin was exposed. Bed bug bites appear later, in lines or clusters on the upper body and arms, and only after time spent in one bed.

The table above sets the four side by side. If the bites are around the ankles and there is a cat or dog in the house, read about flea bites on people first, and if the pets are the source, flea treatment deals with the house as well as the animal. Health New Zealand also compares bed bug bites to sandfly bites, which in New Zealand come from small black biting flies outdoors, not from anything living indoors.

Some rashes that look like bites are not bites at all. Scabies, for example, is caused by a mite that lives in the skin and is diagnosed and treated by a doctor, so if the marks do not fit any of the patterns above, your GP is the right person to see rather than a pest firm.

First aid for bed bug bites

Left alone, most bed bug bites fade without treatment, and the CDC's guidance for clinicians says minimal care for the itch is usually all that is needed. Wash the area, hold a cool damp cloth or an ice pack wrapped in a tea towel on it for up to ten minutes at a time, as healthify suggests, and try hard not to scratch. If the itch keeps you awake, ask a pharmacist about an anti-itch cream or an antihistamine.

Toothpaste, vinegar and similar home remedies come up often. Nothing reliable shows that they help, and some sting or irritate skin that has already been broken by scratching, so a pharmacist is the better call.

When bites need a doctor rather than a pharmacist

See a doctor, or call Healthline free at any hour on 0800 611 116, if bites have not improved after two weeks, if the redness keeps spreading or becomes more painful, if there is pus, or if a bite is near the eye. These are the points healthify lists. Spreading redness and heat can mean a skin infection such as cellulitis, which DermNet NZ lists among the complications and which may need antibiotics.

Call 111 straight away for a swollen face, lips or throat, difficulty breathing, or feeling faint. A severe allergic reaction, anaphylaxis, is very rare with bed bugs, but Health New Zealand treats it as a medical emergency.

Bites but no bugs: what to do before anyone treats

Do not spray, do not move rooms, and do not throw out the bed on the strength of bites alone. Check the bed first, then stand each leg in an interceptor cup and move the bed out so no part of it touches the wall, which leaves the cups as the only way up. Two weeks of empty cups and a careful search tell you far more than the bites do.

We have written up a step-by-step check of the bed and room and what each stage of a bed bug looks like, with sizes. If the search turns up nothing and the bites carry on, book an inspection that confirms it either way. If we find no evidence, we say so and we do not treat.

Questions

Bed bug bite questions

How long do bed bug bites last?

Most settle over several days to a week or so without any treatment, though a strong reaction can take longer and scratching slows healing. Marks that have not improved after two weeks, or that are getting redder, hotter or more painful, are a reason to see a doctor rather than wait. New bites appearing all the while means the source is still there.

Do bed bugs spread disease?

They are not known to spread disease to people, according to the CDC, and DermNet NZ says the same. The real problems are the itch, skin broken by scratching that can become infected, lost sleep and a great deal of worry. Those are reasons to deal with an infestation promptly, but not reasons to fear an illness from the bites themselves.

Does showering get rid of bed bugs?

No. Bed bugs do not live on people. They feed for a few minutes and go back to the bed frame, the mattress seams or the skirting, so a shower removes none of them. Washing bedding and clothes hot and then drying them on high heat does help, because the dryer's heat kills any bugs and eggs in the fabric.

My partner sleeps in the same bed and has no bites. Can it still be bed bugs?

Yes. Many people show no reaction to bed bug bites at all, with DermNet NZ putting it as high as seven in ten, so it is quite possible that both of you are being bitten and only one of you is marking. Check the bed itself rather than comparing arms.

Can I stop bed bugs biting while the house is being treated?

Mostly, yes. Keep sleeping in the same bed, put encasements on the mattress and base, stand the bed clear of the wall on interceptors, and tuck the bedding in so nothing trails to the carpet. Insect repellents are not a fix. Moving to another room only spreads the problem.