Because most spider bites don't fully penetrate human skin, they usually cause only mild reactions. However, black widow and brown recluse spider bites can cause serious reactions and need immediate care. Allergic reactions can happen but are rare.
Signs and Symptoms
Of a brown recluse spider bite:
red blister in the center with surrounding bluish discoloration around the bite
swelling or redness around the bite
development of pain around the bite within 2 to 8 hours