Spider bite

Disclaimer These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline.  Read the full CAHS clinical disclaimer.

Aim

To guide PCH Emergency Department (ED) staff with the assessment and management of spider bite in children.

Background

• The majority of spider bites in Western Australia are benign.
• Red Back Spider (RBS) envenomation (latrodectism) can be very painful but is non-life threatening¹.

Red-Back Spider (Latrodectus hasselti)

• Red-back spiders are usually found in dark, dry places. They have small bodies approximately 1 cm in length with characteristic red marking.
• The main symptom is pain, which builds over minutes to hours and may last for days.
• RBS antivenom should be considered for cases of persistent pain or distress after adequate analgesia and should only be administered after consultation with an ED consultant or a clinical toxicologist^1,2,3.

Signs and symptoms

Consider the diagnosis in any child with abrupt onset of inconsolable crying, abdominal pain or priaprism.

Local and regional features

• Solitary bite manifesting as single papule/pustule/wheal; multiple lesions reduce likelihood
• Localised pain, which may spread proximally to regional lymph nodes.
• Localised sweating and piloerection, which may spread to unusual areas (e.g. below both knees)
• Paraesthesia, weakness and muscle spasms may also be present

Systemic

• Irritability, agitation or lethargy and malaise
• Nausea, vomiting and abdominal pain
• Hypertension, fever and priapism may also occur
• Rarely, myocarditis and rhabdomyolysis

Investigation

Not required unless concerns of severe systemic response (perform CK/ECG).

Management

First aid⁴

• Wash and clean bite site with antiseptic.
• A cold compress may offer some relief. Apply for a maximum of 20 minutes.
• A pressure immobilisation bandage is not recommended and may increase pain.
• Check the patient's tetanus status.

Analgesia

• Simple analgesia such as paracetamol or ibuprofen should be prescribed regularly.¹
• Opiates such as intranasal fentanyl or oxycodone immediate-release may be required.
• Note: the aim is for a reduction in pain to acceptable levels, not a pain free state. Only 25% of patients have a reduction in pain 2 hours post bite and 50% at 24 hours.

Antivenom

• Use of RBS antivenom has decreased dramatically since the RAVE II study questioned its efficacy. Most clinical toxicologists now restrict its use to cases refractory to standard analgesic regimes.^1,2,3
• Anecdotal experience at PCH suggests that it may be beneficial in young children and a recently published retrospective case series is suggestive of some benefit in the paediatric population. ^6,7,8
• All cases of redback spider envenomation should be discussed with an ED consultant. Consider seeking input from the duty toxicologist at the WA Poisons Information Centre: 13 11 26.

Administration of Antivenom9

Administer in a monitored area with facilities to treat anaphylaxis readily available. A full set of observations should be done at baseline, 15 minutes, 30 minutes then hourly for 2 hours. Record on the Observation and Response Tool, with additional observations recorded on the Clinical Comments Chart. Give 2 vials. Dilute 1 in 10 in sodium chloride 0.9% and give via the intravenous (IV) route over 20 minutes. Note: Dose of anti-venom is not dependent on the age or weight of the child.

Adverse Reactions

Hypersensitivity reactions (<5%) are usually limited to a rash. Anaphylaxis is rare and should be managed by stopping the infusion and following anaphylaxis guidelines. Serum sickness (< 10%) occurs 5-10 days post anti-venom administration and presents with fever, rash, joint pains and myalgia. It responds well to 7 days of oral prednisolone.1 Prophylaxis is NOT required.

Discharge

• Suitable for discharge once there is adequate pain control. Ensure sufficient analgesia supply for 5 days.
• If Antivenom is administered, observe for at least one hour and provide information on serum sickness (present for assessment if fever, rash, joint pain developing over the subsequent 14 days).

Funnel-web Spiders

• No species are found in Western Australia. Toxidrome mimics organophosphorus poisoning. Management of Funnel-web envenomation differs, including the recommendation to USE a pressure immobilisation bandage. Consult clinical toxicologist.

Other spider bites and 'Necrotising Arachnidism'

• Many spider bites may be associated with local irritation and inflammation; symptomatic treatment with analgesics and antihistamines for itch is usually adequate.
• The white-tailed spider (Lampona cylindrata) was long implicated in medical literature and media reports as causing skin necrosis and ulceration. However, spider bite in Australia is an extremely uncommon cause of ulceration and should only be considered at the end of a long list of other differential diagnoses including trauma, infections and vasculitis¹⁰.
  • Prospective studies have failed to support the association between Australian spiders and such lesions.
  • Even if a skin ulcer is thought to have been the result of a spider bite, treatment is symptomatic with analgesia, elevation and good wound care.
  • Rarely, the input of a plastic surgeon may be required for wound debridement and skin grafting.

References

1. Spider Bite. In: Therapeutic Guidelines [digital]. Melbourne: Therapeutic Guidelines Limited; 2021 Mar. Topic | Therapeutic Guidelines (health.wa.gov.au) accessed May 2025
2. Isbister GK Brown SG, Miller M, et al.. A randomised controlled trial of intramuscular versus intravenous antivenom for latrodectism – the RAVE study. Quarterly Journal of Medicine 2008; 101:557-565
3. Isbister GK, Page CB, Buckley NA, et al.. Randomised controlled trial of intravenous antivenom versus placebo for lactrodectism: the second redback antivenom evaulation (RAVE II) study. Annals of Emergency Medicine 2014; 64:1-9
4. First-aid management of bites and stings. Western Australian Poisons Information Centre. October 2021. Accessed Aug 22. Available from: 6674063A8BF94460A7EE9B5B417338EC.ashx (health.wa.gov.au)
5. Fairbrother SL, Borland ML. Re: Redback spider bites in children in South Australia: A 10-year review of antivenom effectiveness. Emerg Med Australas, 2022; 34: 301-302
6. Cocks J, Chu S, Gamage L, Rossaye S, Schutz J, Soon AWC. Redback spider bites in children in South Australia: A 10-year review of antivenom effectiveness. Emerg Med Australas. 2022;34(2):230-236
7. Downes MA, Lovett CJ, Berling I, Isbister GK. Re: Redback spider bites in children in South Australia: A 10-year review of antivenom effectiveness. Emerg Med Australas. 2022;34(2):297-298
8. Cocks J. Response to Re: Redback spider bites in children in South Australia: A 10-year review of antivenom effectiveness. Emerg Med Australas. 2022;34(2):298-299
9. Australian Medicines Handbook on line: Red back spider antivenom - Australian Medicines Handbook (health.wa.gov.au) accessed May 2025
10. Ibister GK, Gary MR. White-tailed spider: a prospective series of 130 definite bites by the Lampona species. Medical Journal of Australia 2003; 179:199-202

Endorsed by:	CAHS Drug & Therapeutics Committee	Date:	July 2025
		Review date:	May 2028

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