Which Spider Bites Cause Blisters?

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Spiders that are venomous to humans and whose bites may cause blisters include the Brazilian wandering spider, Australian funnel-web spider, widow spider, false black widow, six-eyed sand spider, recluse spider, mouse spider, tarantula, yellow sac spider, hobo spider, white-tailed spider and sun spider. In some cases, blisters may be caused by the spider’s venom, and in others, the damage is caused by the spider’s jaws.

Though nearly all spiders inject some sort of venom when they bite, very few of these toxins are considered medically significant to humans. Of those that are considered toxic, only the Brazilian wandering spider, the funnel web spiders, some of the widow spiders, the Chilean Recluse spider and the Chinese bird spider, which is a type of tarantula, have caused fatalities. The bites are much more dangerous to small children and the elderly. A non-fatal bite from these spiders is still likely to cause local tissue damage, however, possibly including blisters.

The other spiders listed may or may not cause tissue damage and blisters when they bite. Of these, the recluse spiders, particularly the brown recluse, are most notorious for causing tissue necrosis, but this problem actually only occurs in a small minority of recluse bites.

Blisters may also be caused indirectly by rubbing tissue that has been irritated by an otherwise harmless bite.