It can be difficult to know if a bite from a spider is dangerous or not. This article explains the best first aid treatment depending on the type of spider involved.

It’s also important to be aware that bites from spiders can cause a severe allergic reaction (anaphylaxis) in some people. Learn more about first aid treatment for severe allergic reactions in the ‘anaphylaxis’ section below.

Different types of spider bite

For medical purposes, there are 3 types of spider:

• Big black spiders include funnel-web spiders and any large, black-looking spider (which may actually be a funnel-web spider).
• Redback spiders are fairly easy to identify and their bites do not have rapidly developing or life-threatening effects, but many cause significant pain and other problems in the body.
• All other spiders in Australia are more or less harmless.

If you’ve been bitten by a big black spider, treat it as a medical emergency. Call triple zero (000) and ask for an ambulance.

Big black spiders

Redback spiders

First aid for a big black spider’s bite

Bites from a funnel-web or mouse spider can be very dangerous. Provide emergency care — including cardiopulmonary resuscitation (CPR) if needed.

If someone gets bitten, help them to stay calm and follow these steps:

• apply a pressure immobilisation bandage (see below)
• ensure the person bitten does not move around
• keep the bitten limb low down
• if possible, bandage the limb from the area of the bite to the hand or foot, then back up to the body
• immobilise the limb by splinting
• do not move the person
• wait for the ambulance to arrive

St John Ambulance Australia has a first aid fact sheet for spiders on its website.

If you can, carefully catch the spider so it can be identified. The Australian Museum has instructions for catching a spider.

Pressure immobilisation bandage

A pressure immobilisation bandage is recommended for anyone bitten by a big black spider. You should firmly bandage the area of the body involved — such as an arm or leg — and keep the person calm and still until medical help arrives.

Follow these steps to apply a pressure immobilisation bandage:

• First, put a pressure bandage over the bite itself. It should be tight and you should not be able to easily slide a finger between the bandage and the skin.
• Next, use a heavy crepe or elasticised roller bandage to immobilise the whole limb. Start just above the fingers or toes of the bitten limb and move upwards on the limb as far as the body. Splint the limb, including joints on either side of the bite.
• Keep the person and the limb completely at rest. If possible, mark the site of the bite on the bandage with a pen.

The Australian Resuscitation Council has a guide to pressure immobilisation bandages on its website.

Anaphylactic shock

Some people occasionally have a severe allergic reaction to being bitten by a spider. Their whole body can react to the bite within minutes, which can lead to anaphylactic shock (anaphylaxis). Anaphylactic shock is very serious and can be fatal.

Symptoms of anaphylactic shock include:

• difficult or noisy breathing
• difficulty talking and/or a hoarse voice
• a swollen tongue
• persistent dizziness or collapse
• swelling or tightness in the throat
• being pale and floppy (young children)
• wheeze or persistent cough
• abdominal pain or vomiting

If someone is experiencing anaphylaxis, call triple zero (000) for an ambulance.

If the person has a ‘personal action plan’ to manage a known severe allergy, they may need help to follow their plan. This could include administering adrenaline via an autoinjector (such as an Epipen) if one is available.

The Australasian Society of Clinical Immunology and Allergy recommends that for a severe allergic reaction, adrenaline is the only treatment. For further information, visit the Choosing Wisely Australia website.

For more information on anaphylaxis, including setting up a personal action plan, go to www.allergy.org.au.

Cardiopulmonary resuscitation (CPR)

In some cases, the person bitten by the spider may need cardiopulmonary resuscitation.

See healthdirect’s page on how to perform CPR for more information.

St John Ambulance Australia has a printable poster on first aid resuscitation procedures.

First aid for other spider bites

For all other spider bites, including bites from redback spiders, apply a cold compress or ice pack (wrapped in a clean cloth), directly over the bite site for 15 minutes to help relieve the pain and reapply as needed. Seek medical assistance if further symptoms or signs of infection develop.