Symptoms and causes


Typically, a spider bite looks like any other bug bite — a red, inflamed, sometimes itchy or painful bump on your skin — and may even go unnoticed. Harmless spider bites usually don't produce any other symptoms.

Black widow spider bites

Signs and symptoms of a black widow spider bite may include:

  • Pain. Typically beginning within an hour of being bitten, pain generally occurs around the bite mark, but it can spread from the bite site into your abdomen, back or chest.
  • Cramping. Abdominal cramping or rigidity can be so severe that it's sometimes mistaken for appendicitis or a ruptured appendix.
  • Sweating. Excessive sweating can occur.

Brown recluse spider bite

The pain associated with a brown recluse spider bite typically increases during the first eight hours after the bite. You may also have fever, chills and body aches. The bite usually heals on its own in about a week. In a minority of cases, the skin at the center of the bite can become dark blue or purple and then evolve into a deep open sore (ulcer) that enlarges as the surrounding skin dies. The ulcer usually stops growing within 10 days after the bite, but full healing can take months.

When to see a doctor

Seek prompt medical care in the following situations:

  • You are unsure whether the bite was from a poisonous spider.
  • The person who was bitten experiences severe pain, abdominal cramping or a growing ulcer at the bite site.
  • The person who was bitten is having problems breathing.

Your doctor may recommend a tetanus booster shot if you haven't had one in the last five years.


Severe spider bite symptoms occur as a result of injected spider venom. The severity of symptoms depends on the type of spider, the amount of venom injected and how sensitive your body is to the venom.

Risk factors

Although dangerous spider bites are rare, your risk of being bitten increases if you live in the same areas that the spiders do and you happen to disturb their habitat. Both black widow and brown recluse spiders prefer warm climates and dark, dry places.

Black widow habitat

Black widow spiders can be found throughout the U.S. but more so in the southwestern states. They prefer to live in:

  • Sheds
  • Garages
  • Unused pots and gardening equipment
  • Woodpiles

Brown recluse habitat

Brown recluse spiders are found most commonly in the southern Midwest and in limited areas of the South. Recluses are so named because they like to hide away in undisturbed areas. They mostly prefer to live indoors, in places such as:

  • The clutter of basements or attics
  • Behind bookshelves and dressers
  • In rarely used cupboards

Outside, they seek out dark, quiet spots, such as under rocks or in tree stumps.


Very rarely, a bite from a black widow or brown recluse spider may be deadly, particularly in children.