Is there a way to know if a spider bite is poisonous our not?

Information: Most likely by knowing the type of spider. Also by the healing pattern. The reaction to a poisonness spider bite is much larger and more intense than non poisonness bites.

Not necessarily: If you think a spider bit you & you have fever, severe pain (can be felt at bite site & possibly chest, back or abdomen); abdominal cramping /rigidness or ulceration of skin at site - those are clues if may be poisonous. However, some people have very mild reactions to poisonous spider bites- so you may not be able to differentiate.