Treating spider bites
Only some spiders are able to bite humans. There are 3 species of spider to avoid — the katipō, the redback and the whitetailed spider.
Whitetailed spiders
The whitetailed spider is more common than the katipō and redback. It is often found in houses, including on the walls and ceilings.
Whitetailed spiders will bite if provoked. But in most cases the bite will cause little harm.
Whitetailed spider bites are not considered poisonous to humans. A recent Australian study has shown no evidence linking necrotic ulcers (destroyed skin) to whitetailed spider bites.
Symptoms of a whitetail spider bite
The whitetailed spider bite can be painful. You may have some:
- swelling
- redness
- itchiness
- a burning feeling at the bite site.
These symptoms will go away, and there are no long lasting effects.
How to treat whitetailed spider bites
If you think you have been bitten by a whitetailed spider you can treat this with simple first aid. These spiders do not cause skin damage or ulcers. If you think you have been bitten, clean the wound with antiseptic, or warm soapy water. Put ice on the skin to reduce any pain or swelling — do not put this directly on the skin. Wrap the ice in cloth to prevent cold burns.
Contact your healthcare provider if the bite area:
- is very red
- is painful
- blisters
- appears infected
- forms an ulcer.
If you need advice on first aid and bite treatment, call the National Poisons Centre on 0800 764 766
Katipō and redback spiders
The katipō and the redback spider are the only venomous spiders found in Aotearoa New Zealand. Only the adult females are capable of biting humans. Bites from both species are extremely rare.
Symptoms of a katipō spider bite
Symptoms of a katipō bit include:
- pain at the bite site which spreads to other areas and becomes more intense
- sweating
- difficulty breathing
- abdominal cramps
Symptoms of a redback spider bite
Redbacks will only bite when disturbed or trapped in clothing. Their bite will feel like a sharp pinprick. Symptoms can include:
- redness at the bite site
- pain
- sweating
- stomach pain
- aches in muscles and joints
- feeling sick and throwing up
- increased heart rate
- increased blood pressure.
Generally these occur quite soon after being bitten. Serious reactions are uncommon and are not likely to develop in less than 3 hours. Venom is not always introduced with the bite. If it is, most reactions to the venom are moderate.
If you are concerned:
-
call the National Poisons Centre on 0800 764 766
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call 111 in an emergency and ask for an ambulance.
How to treat a katipō or redback spider bite
Mild symptoms can generally be managed at home with oral pain relief such as paracetamol and ibuprofen
If symptoms become more severe seek medical attention straight away. Hospitals can provide safe and effective treatment (anti-venom).
If you think you have been bitten by a katipō or redback spider
If you think you have been bitten, clean the wound with antiseptic, or warm soapy water. Put ice on the skin before travelling — do not put this directly on the skin. Wrap the ice in cloth to prevent cold burns.
Do not apply pressure to the bite or drink alcohol after being bitten.
Assessment of the potential public health impacts of venomous spiders
In 2000 black widow spiders were detected in several shipments of imported grapes from California. This prompted a risk assessment being undertaken and import controls being applied. The controls included an import health standard for table grapes that contained pre- and post-border measures to manage the risk from venomous spiders.
The risk assessment has now been updated. It assesses the potential human health risks from both:
encountering spiders in table grapes
establishment of these spiders in New Zealand.
The main changes from the original health risk assessment include updating the:
- references, noting the presence of redback spiders in New Zealand — limited to Central Otago
- recommended treatment advice — antivenom is no longer routinely recommended.
It also updates the countries which export grapes to New Zealand, and interception data showing the efficacy of current import controls.
The updated health risk assessment finds that, based on the low level of post-border detection of these species, current pre-border methods are enough to prevent the introduction of venomous spiders associated with imported table groups.
