Even if venom is injected, the bite of the brown recluse rarely causes systemic reactions. It usually effects only the tissue surrounding the bite. Although this local damage is not fatal, significant tissue damage around the bite may occur and may require surgical intervention to correct.

The venom of the brown recluse contains 8-10 proteins. The most significant is sphingomyelinase D which may be largely responsible for dermatonecrosis (plugging of venules and arterioles by microthrombotic leukocytes and platelets) and hemolytic anemia (direct RBC attachment leading to lysis).

For the benefit of any English speaking readers, I will translate that last paragraph. The venom of the brown recluse contains nasty stuff (that long "s" word) that kills the skin and subcutaneous tissue cells (dermatonecrosis) by plugging up the small vessels that supply blood to them. These clogs are made up of platelets and damaged white blood cells. In addition, the venom attacks the red blood cells, eventually causing them to break and die (lysis) which further reduces perfusion to the skin cells and surrounding tissues.

This causes areas of the skin and tissues surrounding the bite to die. This tissue destruction may continue until the envenomated tissue is surgically excised (although I should note that recent studies have proposed that surgical excision may not be the best way to deal with these bites). After a while, this tissue drops off leaving a rotting open wound that resists healing and may produce severe scarring. Bites that occur in areas of the body with a lot of fatty tissue result in worse scarring than in areas of muscle.

The following is a rough timeline of the sequence of events following a brown recluse bite.

Often the initial pain (the bite itself) is described as less painful than a bee sting and may even go unnoticed or ignored by the patient. Within 1 to 2 hours the intensity of the pain will increase and may become excruciating within a few hours after the bite. Within 2-8 hours pain continues to intensify and erythema develops, followed within 1 to 2 days by a central blister at the site of the bite with a surrounding area of vasoconstriction. Over the next 24 to 72 hours, the rash surrounding the blister (erthema) expands and the central blister may turn purple or black as necrossis of the skin occurs. As the tissue dies eschar forms (dead skin) which drops off in 7 to 10 days. As we have said, the resulting ulceration is resistant to healing and may continue to grow. The following picture illustrates a brown recluse bite after about 8 hours.

Blister, necrosis and central area turns bluish (seen above), sinks below skin level, with surrounding areas of ischemia (white) and inflammation (red).

The following photos show a brown recluse bite at different stages in this process.

The preceeding three photos show a brown recluse bite after ulceration and then at two months and finally at two and a half months months. Note that even after 63 days the wound has not completely healed.

The photo above shows an extreme example of just how bad these bites can get.

This is the posterior thigh and lower leg of a person suffering a particularly severe bite. Most bites are not this severe.

Although most of the damage from a brown recluse bite is confined to the area around the bite, some mild system wide reaction is to be expected. A frequent complex of signs/symptoms: pain, redness, itching, headache. Rash is a fine macular eruption over entire body. With non-systemic envenomations, this rash will usually disappear within two to three days. Envenomations usually cause a general body-wide reaction but are not considered systemic envenomations.

Non-systemic envenomations will produce some general signs and symptoms that are to be expected.

Symptoms: 82% pain Signs: 94% erythema

47% pruritus (hives) 41% cellulitis

41% malaise (feel Bad) 29% rash

35% chills/sweats 29% blister