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. Many skin sores look the same but have other causes, such as a bacterial infection. Bites from some spiders, such as widow spiders and recluse spiders, might cause serious signs and symptoms. Widow spider bites Signs and symptoms of a widow spider bite can include: 
Redness, pain and swelling. You might have pain and swelling around the bite, which can spread into your abdomen, back or chest.
Cramping. You might have severe abdominal rigidity or cramping, which is sometimes mistaken for appendicitis or a ruptured appendix.
Nausea, vomiting, tremors or sweating. You might experience nausea, vomiting, tremors or sweating alone or in combination.
 Symptoms can last 1 to 3 days. Recluse spider bites Signs and symptoms of a recluse spider bite can include: 
Increasing pain over the first eight hours after the bite
Fever, chills and body aches
A bite wound with a pale center that turns dark blue or purple with a red ring around it
A bite wound that grows into an open sore (ulcer) with the skin around it dying
