Myth: You can always tell a spider bite because a spider leaves two punctures.
Fact: There is a germ of truth in this idea, but only a very tiny germ. Spiders do have two venom-injecting fangs and typically bite with both at the same time. However, in any spider smaller than a tarantula, the entry points of the two fangs will be so close together that there is little if any visible separation. Also, the fangs are so slender and sharp that the actual entry points are all but invisible.
When you have a "bite" with two separated marks, it is either caused by a bloodsucking insect that has bitten twice (a common occurrence), or is a double skin eruption arising from one disease condition or arthropod bite, also a common occurrence.
Information on this web site is not a substitute for professional medical advice, and should not be used to diagnose or treat a medical or health condition. You should consult a physician as to any symptoms that may require diagnosis or treatment. Genuine spider bites can sometimes require medical attention, but beyond that, several medical conditions commonly mistaken for spider bite can be even more serious. If you have what appears to be a serious spider bite, please contact your health care provider or local emergency services. If you have the actual spider that bit someone, always save it for identification by a professional arachnologist.