Spider Bite Identification: What to Notice and When to Worry

Many marks people call spider bites turn out to be other insect bites or skin infections. Unless a spider was seen biting, the cause is usually uncertain — so focus on how the mark behaves, not the name.

Take seriously a mark that becomes rapidly larger, very painful, darkened or blistered, or is joined by fever, muscle aches, or feeling unwell. These can indicate infection or a reaction that needs prompt care.

Get emergency help for trouble breathing, facial or throat swelling, fainting, or a spreading dark wound. When in doubt about a worsening bite, contact a healthcare professional rather than waiting.