Spider Bites in Arizona: Both Kinds Are the Opposite of What You Expect

Call 911 for trouble breathing, chest pain, collapse, or a child who is not right. Otherwise call Poison Control on 1-800-222-1222 — and note that Arizona Poison Control says medical treatment is always advised when a brown spider bite is suspected.

Two spiders in Arizona are worth knowing about, and they present in opposite ways — neither of them the way people assume a dangerous bite must feel.

The black widow hurts, and there is almost nothing to look at. The brown spider barely hurts, and the wound arrives later. Between them they cover both ways a person talks themselves out of being seen: nothing to show a doctor, or nothing that felt bad enough at the time.

So the single most useful thing on this page: how the bite felt is not how serious it is.

The black widow

What she looks like, from the Arizona Poison and Drug Information Center: “A mature female is a globe-shaped, black, shiny spider with a red or orange marking or hourglass on the underside of her abdomen.”

What the bite does. Poison Control describes it in two stages, and the second is the one that matters:

“The initial sensation may be painful, with little local reaction. Later, pain, cramping and stiffness may appear in the shoulders, back, chest or abdomen.”

Read where that cramping goes. Not the hand that was bitten — the shoulders, back, chest and abdomen. Poison Control also names “nausea, vomiting, headache, anxiety and high blood pressure.”

So the picture is a painful bite, a site that looks like nearly nothing, and then a person with chest or abdominal cramping who may well not connect the two events at all.

Which produces one rule worth stating plainly

Chest pain is an emergency whatever you think caused it.

If you have chest pain, abdominal pain, or cramping you cannot explain, the answer is to be seen — not to sit at home working out whether a spider could account for it. A spider bite you remember does not make chest pain less of an emergency, and what to do about chest pain does not change because there is another possible explanation.

Working backwards from a theory is how people arrive late.

First aid, and the age that changes the answer

Poison Control’s first aid for a black widow bite: “Clean the site well with soap and water. Apply a cool compress over the bite location and keep the affected limb elevated to about heart level.”

And the threshold to know:

“Treatment in a medical facility may be necessary for children less than 5 years old or for adults with severe symptoms.”

Children under five are named specifically. A small body and the same amount of venom is the same arithmetic that runs through scorpion stings — so for a small child, call 1-800-222-1222 immediately and expect that being seen may be the answer.

The brown spider, which is a slower and stranger problem

What it looks like: “light tan to brown with a violin-shaped marking on the back of the head-chest region. With legs extended, it is approximately the size of a nickel to a quarter.”

Where it is: “non-aggressive spider is found in dry, littered and undisturbed areas such as closets, woodpiles and under sinks.” Which describes the places people reach into without looking — and “non-aggressive” is the point. These bites happen when a hand arrives, not when a spider does.

How it unfolds, and the timings are Poison Control’s:

At the time: “a patient experiences little or no local pain at the time of the bite.”

Within hours: “localized pain may develop in the first few hours.”

Within the first day: “Systemic flu-like symptoms, including nausea, vomiting and malaise may appear in the first 24 hours.” Feeling generally unwell is part of it.

Then the wound: blisters may develop “as early as 12 hours to several days following the bite”, evolving into what Poison Control calls the classic “bulls-eye lesion.”

Twelve hours to several days. So the bite that was not worth mentioning on Tuesday can be a wound that needs treating by Friday, and by then most people have stopped connecting it to the cupboard they reached into.

And for the brown spider, the instruction is unusually firm

“Medical treatment is always advised when a brown spider bite is suspected.”

Always advised, on suspicion. That is stronger than almost anything else on this site, and it is Poison Control’s wording rather than ours. Their other instruction is equally plain: “Call 1-800-222-1222 if you think you have been bitten.”

You do not need to have seen the spider, and you do not need the wound to have appeared yet.

Where to go

Call Poison Control on 1-800-222-1222 — free, any hour, and they will tell you whether this needs a hospital.

Call 911 for trouble breathing, chest pain, collapse, a seizure, or a small child who is lethargic, cannot be settled, or is not behaving normally.

Come to an emergency room for a suspected brown spider bite, for a black widow bite in a child under five, for severe or spreading pain, for cramping in the chest, back or abdomen, or for a sore that is enlarging.

Our emergency rooms treat envenomation, they are open every hour of every day, and they are walk-in. Go to the nearest one, and if another emergency department is closer to you, that one is the right answer tonight.

If you are unsure, come in — this list is not exhaustive and you are not expected to identify a spider or stage a wound yourself.

Not getting bitten in the first place

All of this follows from where these spiders actually are:

Gloves for woodpiles, boxes, and anything stored outdoors. Both spiders like undisturbed places, and your hand is what disturbs them.

Look before reaching into a closet floor, under a sink, behind stored boxes, or into a shed.

Shake out shoes, gloves and clothing that have been on the floor or in storage — the same habit that works for scorpions.

Clear clutter where you can, particularly in garages and closets. “Dry, littered and undisturbed” is a description of a habitat, and it is one you can change.

Questions people actually ask

I did not see what bit me. That is the normal situation, and it does not change what to do. Call 1-800-222-1222, describe what you feel and what the site looks like, and let them decide. Identification is not the reader’s job.

I have a spreading sore and no memory of a bite at all. Get it seen. Plenty of things produce a spreading sore and a spider is only one of them, and several of the others need treating promptly. This page is not going to tell you it is a spider.

The bite hurt a lot and there is nothing to see. That is the black widow pattern described above. Call Poison Control, and go if cramping or stiffness starts in the shoulders, back, chest or abdomen.

It did not hurt at all and now it is blistering two days later. That is the brown spider pattern, and their instruction is that treatment is always advised on suspicion. Be seen.

Is a house spider dangerous? Most spiders here are not the two above, and most bites are unremarkable. The reason this page exists is that the two that matter do not announce themselves — so the route is a phone call rather than a judgement.

Should I catch it? No, and do not go back for it. A photograph from a safe distance is fine if one is easy; a second bite is not worth an identification.

---

Call Poison Control any hour on 1-800-222-1222, and be seen for any suspected brown spider bite. Call 911 for chest pain, trouble breathing, or a small child who is not right. Both of our emergency rooms are open 24 hours a day, every day of the year — walk in, no appointment and no referral. Find your nearest emergency room →

Related reading: scorpion stings in Arizona · rattlesnake bites in Arizona

Sources

32. Bees, Spiders & Other Bugs — Arizona Poison and Drug Information Center. https://azpoison.com/venom/bees-spiders-other-bugs

This article is general information, not a diagnosis. It gives no doses. If you are unsure, come in — this list is not exhaustive and you are not expected to identify a spider or assess an envenomation yourself. If it might be an emergency, treat it as one and call 911.