Spider bite pictures

Before the photographs, the thing that matters most: most marks blamed on spiders are not spider bites. A single painful red lump is far more often a skin infection, and the two are hard to tell apart in the first day or two. The photographs below are real spider bites, but they are the severe end of the range — the ordinary case is one small mark that heals in a week and never gets photographed.

What a spider bite looks like

The ordinary case, which is nearly all of them: one red mark a few millimetres across, slightly raised, sore or itchy rather than truly painful, sometimes with two puncture points a short distance apart if the spider was big enough to leave them. It is at its worst within a day or two and fades over the week after that, leaving nothing behind. No rash around it, no fever, and no second mark — spiders bite once, defensively, and then leave.

Where it appears is part of the description. A spider bites when it is trapped against skin, so the marks turn up on a forearm, a hand, a lower leg, or under clothing at the waistband or sock line — where something got pressed rather than where something was hunting. A line or cluster of marks on a covered area is a different story and usually a different animal; bed bug bite pictures show what that pattern looks like.

That description is short because there is not much to it, and the shortness is the useful part. A mark doing more than this — spreading, hardening, breaking down, or still worsening on day three — is doing something an ordinary spider bite does not do, and the question stops being which spider and becomes what else is this.

These are photographs of real bites. All four are documented spider bites: three from a brown recluse at two months and at four months, and one white-tailed spider bite from Australia. Published under CC BY or public domain, with the photographer, the licence and the source file named beneath each one. Bites that look like this are uncommon.

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What the photographs are not showing

There is no photograph on this page of a typical spider bite, and that is not an oversight. A typical spider bite is a red dot that itches slightly for a few days; nobody photographs it and it would tell you nothing if they did. The wounds above took weeks to develop and required surgical removal of dead tissue in one case. Judging your own mark against them will mislead you in both directions — it will frighten you if the mark is ordinary, and it will reassure you on day one if it is going to become serious, because on day one these looked ordinary too.

The stages, day by day

A single photograph is the weakest evidence there is about a bite, because the marks that heal and the marks that do not look the same at the start. What separates them is direction over three days, and that is something you can watch for nothing.

1. First hours. Frequently nothing. Most people never feel the bite and only notice the mark later, which is why "when did this happen" is usually unanswerable and not worth agonising over.
2. Day one. A red or pink mark, firm to the touch, itchy or sore. Some swelling around it. This is the peak for an ordinary bite reaction, and by the end of the day it should be no worse.
3. Day two to three — the turn. The finding that matters. A bite reaction has begun to settle: less red, less sore, edge no further out than yesterday. An infection has gone the other way — wider redness, more heat, more pain, and sometimes a soft centre coming to a point.
4. Day four to seven. The ordinary bite is fading to a brown or yellowish mark and then to nothing. A recluse bite that is going to progress has a pale, blue-grey or blistered centre by now, and that is a different page: brown recluse bite pictures follows one day by day.
5. Past a week. Anything still present, still sore or still enlarging after a week has stopped being a bite question. Whatever started it, it needs to be looked at.

Photographs taken a day apart from the same distance answer this in a way that no single image can, including any image on this page. A pen line drawn at the edge of the redness makes the comparison exact.

House spider bites

This is the commonest thing people ask this page for, and the honest answer is that there is very little to show. The spiders found indoors across most of the world — the American house spider, the domestic and giant house spiders, cellar spiders — are timid, and a bite from any of them is a red dot that stings briefly and is gone in a day or two. Nobody photographs it, so image searches for it return recluse wounds instead, which is where the fear comes from and why it is misplaced.

Two qualifications, because they are the ones people actually run into. The Australian black house spider does bite, and it is genuinely painful with swelling that can last days and occasionally nausea or sweating — but it does not cause the dead tissue it is widely blamed for. And the hobo spider, for years listed as a cause of necrotic wounds in the northwestern United States, was removed from the CDC's list of venomous spiders in 2017 because the evidence for that never held up.

We have no photograph of a house spider bite on this page. That is not an omission: the mark is a red dot, and a red dot photographed on someone's arm tells you nothing you cannot read in this paragraph.

Geography narrows it more than a photograph does

Recluse and widow spiders each occupy a limited range, and outside it a bite attributed to one is very unlikely to be one. That is checkable rather than a matter of opinion: what bit me, by state ranks the biting species actually recorded where you are, from verified occurrence records, and bites by country does the same internationally.

• Brown recluseCentral and south-central United States. Violin marking on the back, six eyes in three pairs — the marking alone is not enough to identify it.
• Black widowRed hourglass underneath. The bite is a systemic problem rather than a wound.
• Wolf spiderLarge, fast, alarming and frequently blamed. The bite is painful and unremarkable.
• Yellow sac spiderCommonly accused of necrotic bites; the evidence for that is weak.
• Redback spiderAustralia. Pain that builds over an hour rather than striking at once, and sweating at the bite site — two signs no photograph can show.

What to do with a mark you cannot identify

1. Wash it and leave it alone. Soap and water, then a cold compress for the pain. Do not cut it, squeeze it or apply heat.
2. Draw the edge. A pen line at the border of the redness turns "is it spreading?" from a memory test into an observation.
3. Photograph it daily. Same distance, same light. Two frames a day apart say more than one frame ever will.
4. Keep the spider if you have it. Even squashed. It is the only thing that can actually answer the question.
5. Judge on day three. Better means it was a bite reaction. Worse means it needs to be seen, whatever caused it.

The comparison that does the most work here is spider bite versus infection, and signs of an infected bite sets out the specific findings to look for.