White-tail spider bite

Although a white-tail spider bite can be painful and cause temporary skin irritation and inflammation, experts now say it’s very unlikely that the white-tail spider is responsible for the hard-to-treat skin ulcers and slow-healing wounds attributed to the spider over the past 30 years. It appears this particular spider’s reputation is undeserved and greatly overestimated.

Symptoms of a white-tail spider bite

A bite from a white-tail spider usually results in temporary symptoms at the site of the bite. This can include:

  • Irritation or a red mark on the skin (including visible puncture marks);
  • Pain or discomfort that is generally mild-to-moderate in severity;
  • Swelling; and
  • Itchiness (either immediately or several days later).

The average duration of symptoms tends to be around 24 hours, but the time taken for symptoms to disappear can vary. Some people only experience symptoms for an hour or two, whereas others may have symptoms (such as a painful red mark on the skin) that last for up to a week.

More rarely, white-tail spider bites may cause:

  • Severe pain (in just over one-quarter of cases);
  • Nausea, vomiting, headache or feeling unwell (in around 10% of cases).

There are thought to be more than 10,000 different species of spiders in Australia. But with the exception of several highly venomous ones – like the redback spider and funnel-web spider that can cause serious illness and possibly death – most spider bites in Australia generally cause relatively minor symptoms.

Do white-tail spider bites really cause a ‘flesh-eating’ wound?

The white-tail spider has often been blamed in media reports and on social media for the development of nasty ‘flesh-eating’ skin wounds that take a long time to heal, or sometimes never completely heal. Some reports even suggest that being bitten by the white-tail spider results in wounds so severe that amputation of an affected body part is necessary. This phenomenon goes by the complicated name of ‘necrotic arachnidism’, which is another way of saying that a patch of skin dies (a process known as necrosis), possibly due to a bite from a spider (which is an arachnid).

However, spider experts now strongly question whether the white-tail spider is the guilty party in these cases of severe skin ulcers. The initial theory several decades ago was that the venom of the white-tail spider resulted in the death of skin tissues. However, later experiments have confirmed that white-tail spider venom is quite weak and does not result in the death of skin cells in laboratory tests.

Support for the innocence of white-tail spiders also comes from the largest study of its kind looking at 130 Australian cases confirmed to be caused by white-tail spiders (proven by capturing the offending spider and having it identified by a spider expert). Although all victims experienced pain and discomfort following the bite, there were no cases of skin ulcers or persistent skin wounds in any of the 130 cases.

So the good news is that – on the basis of the currently available evidence – spider bites of any kind in Australia are very unlikely to cause skin ulcers or slow-healing wounds.

What else can cause slow-healing skin wounds?

Anyone with skin wounds that don’t heal should seek medical attention and be investigated for other causes of skin ulcers and wounds. This can include problems with blood circulation, skin ulcers due to diabetes, secondary infections with bacteria, fungi or viruses, drug reactions, burns (especially chemical burns), physical injury to the skin, some inflammatory skin diseases, and some types of cancer.

How common is a bite from a white-tail spider?

Although the available evidence appears to clear white-tail spiders as the culprit when it comes to skin wounds, it seems that the general public has an unnecessarily high level of anxiety about this particular spider. In a survey of 663 calls made to the Victorian Poisons Information Centre for suspected spider bites, calls about white-tail spiders accounted for more than a quarter of all calls over the course of the year. This is unusual considering that white-tail spider bites generally cause only minor effects. Phone calls about the more dangerous redback spider accounted for almost 70% of calls.

Where do white-tail spiders live?

White-tail spiders live throughout Australia and are often found indoors, so the majority of white-tail spider bites occur indoors, particularly during warmer months (September to April). The spider is most active at night, and in the Australian study of 130 confirmed white-tail spider bites, 75% of bites occurred between 4 PM and 8 AM, primarily from spiders that were in caught up in bedding or on towels and clothing. Around a quarter of white-tail spider bites occurred on the lower arms and hands or lower legs and feet.

What should I do if I think I’ve been bitten by a white-tail spider?

It can be difficult to tell what type of spider has bitten you unless the spider has been seen at the time the bite occurs. If the spider can be safely captured in an escape-proof container, this may help later identification by an expert.

Unlike many types of spiders that look similar to each other, white-tail spiders are easier to identify because of a distinctive white spot on top of the end of their abdomen. The abdomen is also longer (almost cigar-shaped) compared to some other spiders, such as the redback spider, that have a round abdomen.

If there is a possibility that a spider bite is due to a redback spider or a funnel-web spider, you should seek immediate medical attention. Bites from these spiders can be serious and potentially deadly. You may require treatment with anti-venom (particularly for bites from a funnel-web spider).

In contrast, the venom of white-tail spiders is weak, so for bites from this and many other species of spider, temporary treatment of the symptoms may be all that is required. This can include simple remedies such as:

  • Cleaning the affected area with a disinfectant or antiseptic;
  • Applying a cold pack or ice wrapped in a towel to the bitten area;
  • Taking a pain reliever to reduce pain, inflammation and swelling – such as paracetamol (Panadol) or ibuprofen (Nurofen); or
  • Taking an antihistamine to relieve itchiness.

In the Australian study of confirmed white-tail spider bites, only 21 of the 130 patients visited an emergency department or a local doctor, and none required admission to hospital.

In the very unlikely event of skin wounds that are slow to heal after a suspected white-tail spider bite, a doctor may take a sample of tissue from the wound and conduct a full health check to look for other possible causes. Antibiotics may be necessary if the skin becomes infected with bacteria. Very occasionally, skin grafts may be used to help heal chronic skin ulcers.

Last Reviewed: 15 July 2016
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References

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