Tarantulas are large, hairy spiders that possess fangs and venom, prompting questions about their danger to humans. A tarantula can bite, but such incidents are infrequent, occurring only when the spider feels threatened. The bite itself is generally considered medically insignificant for most people, often resembling a common bee or wasp sting. For many species, the primary defensive concern lies not in their fangs, but in their fine, irritating body hairs.
The Truth About Tarantula Bites
A tarantula bite is a purely defensive action, not an act of aggression intended to hunt humans. These spiders will typically retreat or display a warning posture before resorting to a bite. Envenomation usually occurs when the tarantula is roughly handled, squeezed, or unintentionally trapped against the skin.
The physical bite involves two downward-striking fangs located at the ends of the chelicerae (the spider’s mouthparts). These fangs inject venom into the perceived threat. The likelihood and severity of a bite differ between the two major groups of tarantulas.
Species from the Americas, known as New World tarantulas, are less prone to biting, relying instead on a different defense mechanism. In contrast, Old World tarantulas (native to Africa, Asia, and Europe) often lack this alternative defense and are quicker to assume a defensive stance or bite. This difference in behavior is reflected in their venom potency, which is typically milder in New World species.
What Happens After a Bite
When a tarantula bites, the immediate sensation is usually a sharp, localized pain caused by the mechanical puncture of the fangs. This initial pain is often followed by localized symptoms that can last for several hours. Common reactions include redness, warmth, and mild swelling at the bite site, similar to a typical insect sting.
Tarantula venom is a complex mixture of proteins and neurotoxins that is rarely life-threatening to humans. While non-lethal, the venom from some species, particularly Old World varieties, can cause more intense systemic effects. These temporary effects may include muscle cramping, headache, nausea, or localized muscle spasms. Medical attention is necessary only if a person exhibits signs of a severe allergic reaction, such as difficulty breathing, swelling of the throat or lips, or a rapid heart rate.
Urticating Hairs: The Primary Defense
For many New World tarantula species, the primary defensive mechanism is their urticating hairs, not their venom. These are tiny, barbed bristles located in patches on the spider’s abdomen. When threatened, the tarantula uses its hind legs to swiftly scrape or “kick” a cloud of these hairs toward the threat.
The micro-barbs allow these hairs to easily lodge into the skin and mucous membranes, causing intense irritation. Exposure typically results in an itchy, red rash that can persist for days or even weeks. A more serious risk occurs if the hairs enter the eyes or airways, potentially leading to painful inflammation, a condition known as ophthalmia nodosa, and breathing difficulties. The hairs are often a greater health concern for owners of New World tarantulas than the actual bite.
Prevention and Immediate Care
The most effective way to prevent a tarantula bite or exposure to hairs is to never handle wild tarantulas and to respect their space. For pet owners, avoiding rough handling and keeping hands away from the abdomen of hair-flicking species significantly reduces risk. Tarantulas often rear up in a “threat pose” with front legs raised, providing a clear warning before striking.
If a bite occurs, thoroughly wash the wound with soap and water to prevent secondary bacterial infection. Applying a cold compress or ice pack can help reduce pain and swelling at the site. If exposure to urticating hairs occurs, gently applying adhesive tape or wax to the skin can help remove the barbed bristles. Any hairs that enter the eyes or cause severe respiratory distress require immediate medical evaluation for specialized removal and treatment.