Mosquito bite pictures

Nine photographs of real mosquito bites, arranged from the ordinary case to the alarming one. The ordinary case is the first frame and it is what almost everybody has: one raised bump that itches for two days and goes. The frames after it exist because two situations are worth recognising — a reaction far bigger than the bite deserves, and a bite that has been scratched into a wound.

These are photographs of real bites. Eight show the mark on skin and the last shows a mosquito feeding. Published under CC BY-SA or public domain, with the photographer, the licence and the source file named beneath each one; the CC BY-SA frames have been reduced in size by us and are shared on the same terms. What none of them can show is which species bit — that is not written on the skin.

A pale raised bump about five millimetres across on the back of an upper arm, with slight pink colouring around it — One fresh mosquito bite: a pale raised bump with a pink halo, a few millimetres across. Most bites look like this and nothing more. Photo by Marco Bernardini, CC BY-SA 3.0, via Wikimedia Commons. Resized by us and shared under the same licence.

A lower leg with three separate round pink welts, each about a centimetre across, spaced several centimetres apart — Three separate bites on a lower leg. Mosquito bites are usually scattered and unevenly spaced — they do not march in a line. Photo by Vsion, CC BY-SA 3.0, via Wikimedia Commons. Resized by us and shared under the same licence.

A limb with a single broad raised swelling several centimetres across, pink and shiny — A large local reaction: one bite that swelled to several centimetres. This is an exaggerated immune response, not an infection, and it is more common in children. Photo by Vaiiciulaitis, CC BY-SA 4.0, via Wikimedia Commons. Resized by us and shared under the same licence.

Both lower legs and feet seen from the front, covered with dozens of small red spots — Both lower legs after an evening outdoors: dozens of bites at once. The number tells you about exposure, not about the species. Photo by Vaiiciulaitis, CC BY-SA 4.0, via Wikimedia Commons. Resized by us and shared under the same licence.

A broad pink swollen area on a thigh, wider than the hand resting beside it for scale — A severe reaction to a single bite, sometimes called skeeter syndrome: swelling wider than a palm, hot and firm. Worth showing a doctor if it keeps spreading after a day. Photo by Kelvinsong, CC BY-SA 4.0, via Wikimedia Commons. Resized by us and shared under the same licence.

The back of a hand resting on a wooden table, with about a dozen small red spots across it — Bites on the back of a hand. Exposed skin gets bitten — sleeves and trouser legs are the reason bites cluster where they do. Photo by Vinzenz Hediger, CC BY-SA 3.0, via Wikimedia Commons. Resized by us and shared under the same licence.

An ankle and lower calf with many inflamed red spots, several of them scabbed over and surrounded by dry skin — An ankle a few days after the bites, scratched open and crusted. Scratching is what turns a mosquito bite into a wound that can get infected — the bite itself does not do that. Photo by Anna Salmi, CC BY-SA 3.0, via Wikimedia Commons. Resized by us and shared under the same licence.

A forearm with about eight pink raised spots scattered irregularly across it — Scattered bites on a forearm, a day old. The redness fades from the outside in; the itch usually outlasts the mark. Photo by Tom, CC BY-SA 2.0, via Wikimedia Commons. Resized by us and shared under the same licence.

A mosquito standing on the skin of a human hand with its mouthparts inserted, seen from the side — The moment itself. Only females bite, and the bump appears minutes to hours later — which is why people rarely connect a bite to where they were when they got it. Photo by Alvesgaspar, Public domain, via Wikimedia Commons.

Bigger than the frames above? The app reads your photo and says whether the reaction is ordinary. Download free iPhone & iPad · no account

Size is not the question. Direction is

The single most common worry about a mosquito bite is that it has become infected, and the single most common reason people think so is that it got big. Size is a poor signal: a large local reaction to one bite can cover several centimetres, be hot, firm and genuinely alarming, and still be nothing but an immune response to saliva. What separates it from an infection is not how big it is on the day you look, but which way it is heading on the day after.

What a mosquito bite is doing, rather than how big it is
Ordinary bite	Bump a few millimetres across, itchy, peaks within hours, fades over two to three days. Nothing to do beyond not scratching it.
Large local reaction	One bite, several centimetres of firm hot swelling, sometimes with a blister. Worst within 48 hours, then improves. Commoner in children and on first exposure to a local species.
Infected bite	Worse on day three than day one. Redness spreading outward, increasing heat and pain, pus, sometimes fever or a red streak. Nearly always scratched open first.
Dozens at once	Tells you about exposure — an evening outdoors, a still night, standing water nearby — and nothing about the species.
Dark marks weeks later	Post-inflammatory pigmentation from scratching, not scarring and not infection. Commoner and longer-lasting on darker skin.

The bite you scratch is the one that causes trouble

A mosquito bite does not become infected on its own. It becomes infected when fingernails break the skin and carry bacteria into it, which is why the scratched ankle in the photographs looks so much worse than the fresh welt above it despite being the same insect. This is the one part of a mosquito bite that is genuinely within your control, and it is worth more than any cream: how to stop a mosquito bite from itching sets out what actually reduces the urge.

Cold, not heat. A cold compress for ten minutes blunts the itch and the swelling. It works because it slows the histamine reaction, and it can be repeated as often as you like.
Cover it if you scratch in your sleep. A plaster over the bite is more effective than willpower and is the single best way to keep a bite from becoming a wound.
Hydrocortisone for the itch, not for the size. A thin layer of 1% twice a day settles the itch. It does not shrink a large local reaction faster and is not needed for an ordinary bite.
Draw the edge if it is spreading. A pen line at the border turns "is this getting worse?" into something you can see rather than remember.
Judge on day three. Better means it was always just a bite. Worse means it needs to be looked at, whatever started it.

What to put on it is set out in full under bite treatment, and the two questions people ask most have their own pages: hydrocortisone cream for insect bites and antihistamines for bug bites.

Get a photo assessment in the app

Everything above is free to read. The app adds what a page cannot: point your camera at the bite and get an assessment of the most likely cause, a severity read, and a day-by-day care plan — including the specific signs that mean you should be seen.

Download on the App Store — free

iPhone and iPad · Free to download · No account needed

When it is not a mosquito

Scattered itchy bumps on uncovered skin are the commonest presentation of a mosquito bite and also of several other things. The distinction that matters most is bed bugs, because the answer changes what you do next — a mosquito bite is over in a week, an infestation is not: bed bug versus mosquito bites sets the two side by side. Bites on covered skin, bites that appear overnight in the same bed each night, or bites in a line are all arguments against a mosquito.

Bed bug bite picturesBites on covered skin, appearing overnight, plus the fecal staining that settles it when the bites cannot.
Flea bite picturesSmall spots concentrated below the knee, usually with a pet in the house.
Mosquito bites in detailThe species, the timeline, and what a mosquito bite actually does to skin.
What bit me, by stateWhich biting species are actually recorded where you are, from verified occurrence records.

Seek medical care if

Call emergency services now for difficulty breathing, swelling of the lips, tongue or throat, dizziness or fainting, or hives spreading away from the bite.

Redness that keeps spreading on day three, with increasing heat and pain — an infected bite rather than a large reaction.
Pus, a red streak running away from the bite, or fever and chills.
Fever, headache, joint pain or a rash in the days after being bitten in an area with mosquito-borne disease.
Swelling of the lips, tongue or throat, wheezing or dizziness after a bite.
A bite that has not begun to improve after a week, or one in a person with diabetes or a weakened immune system that is not clearly settling.

Common questions

What does a mosquito bite look like?

A raised bump a few millimetres across, pale or pink in the middle with a red halo, appearing within minutes to a couple of hours and itching for two or three days. Bites are scattered and unevenly spaced on skin that was uncovered. There is no line, no cluster pattern and no fixed number — the count tells you how long you stood outside, not which species bit you.

Why is my mosquito bite so big?

Because the reaction is to mosquito saliva, and how strongly you react is individual. A large local reaction — several centimetres of firm, hot, itchy swelling from one bite — is an exaggerated immune response, not an infection. It is commoner in children, in people newly exposed to a local mosquito species, and it tends to lessen over years of exposure. It peaks within a day or two and then settles, which is the feature that separates it from infection.

How do I tell a big reaction from an infected bite?

By what it does over two to three days. A large local reaction is at its worst within about 48 hours and then improves. An infection is worse on day three than on day one: the redness keeps spreading, the skin gets hotter and more painful, and pus, fever or a red streak running away from the site may appear. Almost every infected mosquito bite was scratched open first.

How long do mosquito bites last?

The itch is usually gone in two to three days and the mark within a week. A large local reaction can take a week or two to flatten. Scratched bites take longest because the healing restarts each time the skin is broken, and they are the ones that leave a darker mark for months afterwards, particularly on darker skin.

Can you tell which mosquito bit you from the bite?

No. The mark is your reaction to saliva, not a signature of the species, and no photograph of skin distinguishes an Aedes bite from a Culex bite. What narrows it is where you were and when: species differ by region, habitat and time of day, and that is checkable in a way the mark is not.