SYMPTOMS · RED FLAGS · SAFE TRIAGE

Spider Bite Symptoms: What They Look Like and When to Worry

A skin mark rarely identifies the spider. The person’s symptoms and how quickly they change matter more.

Common local symptoms

Minor bites may cause local pain, redness, itch, swelling or a small blister. These symptoms overlap with mosquito bites, ant bites, dermatitis, boils and early skin infections. Two puncture dots are not reliable proof of a spider bite.

A skin mark is only one part of the assessment

Many suspected spider bites are never confirmed because the spider was not seen biting or identified by an expert. Redness, swelling, itch, tenderness, a blister and even two small dots can occur with insect bites, irritated follicles, minor injuries, dermatitis, boils and infection. A close-up photograph may document change, but it cannot reliably name the cause.

Begin with the event and the person. Was a spider actually seen? Was it a large dark spider in an area where funnel-webs occur? Did pain start immediately? Is sweating localised near the bite, as can occur with redback envenomation? Are symptoms confined to the skin, or is the person developing vomiting, weakness, breathing difficulty, confusion or collapse? Those questions change first aid more than the exact shape of a mark.

Danger signs by pattern

Pattern 1: a mild local reaction

A minor bite may produce local pain, burning, itch, redness or swelling without general illness. Wash the area, apply a wrapped cold pack for up to 20 minutes and monitor. The person should remain able to breathe normally, think clearly and use the affected part without rapidly increasing pain or weakness. Mild does not mean “ignore it”; it means the response remains local and is stable or improving.

Pattern 2: redback-type pain and sweating

Redback envenomation often begins with pain that intensifies and may spread. Sweating can be especially noticeable around the bite. Headache, nausea, vomiting, abdominal discomfort, weakness, muscle spasms or widespread sweating may follow. Do not apply pressure immobilisation. Use a wrapped cold pack and contact the Poisons Information Centre or seek medical care when pain is severe or symptoms are progressing.

Pattern 3: funnel-web or big-black-spider emergency

Immediate severe pain, heavy sweating, drooling, watery eyes, tingling around the mouth, vomiting, muscle twitching, agitation, confusion, breathing difficulty or collapse can indicate severe envenomation. Symptoms may develop quickly, but the correct response starts before they appear: 000, complete stillness, pressure immobilisation and a splint.

Pattern 4: anaphylaxis

Any bite can rarely trigger a severe allergic reaction. Warning signs include difficult or noisy breathing, tongue or throat swelling, wheeze, persistent cough, difficulty speaking, dizziness or collapse. Use an adrenaline autoinjector if available and indicated by the person’s action plan, call 000 and follow the call-taker’s instructions. This pathway is based on the allergic reaction, regardless of spider species.

What an infected bite may look like

Any break in the skin can become infected. Spreading redness, increasing warmth, swelling, pus, worsening tenderness, fever or red streaking require medical assessment. Do not assume that an ulcer or infected-looking lesion proves a spider caused it.

Inflammation and infection are not the same thing

Redness and warmth soon after a bite can be part of local inflammation. Infection becomes more concerning when pain and heat keep increasing, redness expands, pus appears, red streaks develop, nearby glands become tender, fever occurs or the person feels progressively unwell. Infection may follow broken skin, but an abscess or infected follicle may also have been the original problem rather than a spider bite.

Do not squeeze, lance or cut a lump. Do not apply caustic products or cover an actively worsening area with layers of unprescribed creams. Keep open skin clean, use a simple dressing if needed and arrange assessment. Rapid spread, severe pain, fever, immune suppression, diabetes or poor circulation should lower the threshold for prompt care.

Why a dark centre is not proof of venom damage

Online searches often label a black, purple or ulcerated centre as a “necrotic spider bite”. Australian evidence does not support spider bite as a common cause of necrotic ulcers. Tissue damage needs a clinician to consider infection, vascular problems, inflammatory disease, pressure injury, trauma and other causes. Attaching a spider label too early can delay the treatment that is actually needed.

If an ulcer forms, document when it began, how quickly it changed and what treatments were used. Seek medical care rather than continuing to compare photographs. A serious-looking lesion and serious envenomation are not the same process: a funnel-web emergency is recognised by the exposure and rapidly developing systemic pattern, not by waiting for skin breakdown.

When to seek care

• Immediately via 000: suspected funnel-web/big black, anaphylaxis, collapse, breathing difficulty or rapid deterioration.
• Promptly: severe pain, vomiting, widespread sweating, neurological symptoms, fever or spreading infection signs.
• Routine assessment: a persistent lesion, uncertain diagnosis, bite near the eye, or symptoms not improving as expected.

Safe monitoring

Note the time, symptoms and changes. A photo of the skin may help document progression, but do not repeatedly poke, squeeze or mark beyond the edge if that delays care. Keep the person under observation and escalate if their general condition worsens.

Build a simple monitoring record

1. Record the time of the suspected bite and the first symptom.
2. Photograph the area in consistent light with a size reference, without repeatedly manipulating it.
3. Note pain, itch, swelling and whether redness is stable or spreading.
4. Record general symptoms such as nausea, sweating, weakness, dizziness or breathing change.
5. Write down cold-pack use, medicines and advice received.

Monitoring should support a decision, not become a reason to delay it. Call 000 immediately for a suspected funnel-web or big-black-spider bite, anaphylaxis, collapse or breathing difficulty. Seek prompt medical care for severe pain, worsening general symptoms, rapidly spreading inflammation, fever, pus, red streaks or a wound that is not healing.

People who need a lower threshold for review

Young children may not describe symptoms accurately. Older or frail adults and people with diabetes, poor circulation or reduced immunity can have greater consequences from infection or delayed healing. Bites near the eyes, mouth or throat also deserve early advice. Pregnancy, important medical conditions or medicines that affect bleeding or immunity should be mentioned when seeking guidance.

What to tell Poisons Information or a clinician

• Whether a spider was seen biting and whether a safe photograph exists.
• The location, activity and environment where it happened.
• The bite site and the timing of pain, itch, sweating or general symptoms.
• Whether symptoms are local, spreading or affecting breathing, alertness or movement.
• Medical conditions, medicines, allergies and the person’s age.
• First aid and medicines already used.

Body location changes what can be safely done

A cold pack can be used on many local bites, but avoid pressure on an eye and do not place ice inside the mouth. Bites or swelling around the eye, mouth or throat deserve early professional advice because a small amount of swelling can affect important structures. Pressure immobilisation is designed for a limb; do not tightly wrap the chest, abdomen, head or neck.

If a suspected funnel-web bite is on the body rather than a limb, call 000, keep the person completely still and follow the call-taker’s instructions. Do not improvise a constricting band around the torso. If swelling of the tongue or throat, breathing difficulty or collapse occurs after any bite, treat it as an emergency reaction.

Medicines and creams can blur the picture

Write down any antihistamines, pain relief, antibiotics, steroid creams, antiseptics or home remedies used. Some products reduce itch; others can irritate the skin or cause contact dermatitis. Medication can also change symptoms without treating the cause. A clinician needs the full list to interpret progression and avoid interactions or duplication.

Photograph responsibly

Use natural or neutral light, the same camera distance and a ruler for scale. Do not enhance colour or contrast. Avoid sharing identifiable medical photographs publicly when a private record for a clinician is enough. A useful sequence shows change over time; a dramatic macro image without context is more likely to mislead.

After the symptoms settle

If the reaction resolves, no elaborate testing is usually needed. Record any confirmed allergy advice and replenish cold packs or dressings used. If similar unexplained lesions keep recurring, seek clinical review rather than assuming repeated hidden spider bites. Recurrence may be the clue that another skin, environmental or medical cause needs investigation.

Do not let reassurance become neglect

Most local reactions settle, but give the person a clear follow-up plan: what improvement should look like, which changes require a pharmacist or doctor, and which symptoms mean 000. Vague advice to “watch it” is not enough. Name the red flags, record the timeline and make sure the person knows who to call if the pattern changes overnight.

Frequently asked questions

Sources and clinical review

• ANZCOR Guideline 9.4.2: First Aid Management of Spider Bite
• Healthdirect: spider bites
• Queensland Poisons Information Centre: spider bites

Author: Linda Wall — Registered Nurse and First Aid Trainer and Assessor with more than 30 years’ healthcare experience. Sources last checked: July 2026. This is general first aid education, not individual diagnosis or medical advice. For poison advice in Australia call 13 11 26; for an emergency call 000.