It is common for people to be scared of spiders but arachnophobia is defined as the abnormal and persistent fear of arachnids or spiders. These people are scared of even the smallest spiders and exhibit symptoms of anxiety at the sight or mere thought of these creepy, crawly creatures.
This fear may have been brought about by the thought that spiders are venomous and that a single bite can kill. They might have seen in movies that a bite from a Tarantula or Black Widow Spider is fatal thus they made a conclusion in their mind that all bites from spiders are fatal even if they are not. They might have been bitten by a spider also in the past thus contributing to this phobia. This fear could have also arisen in the Dark Ages when they had this notion that spiders were a source of contamination and poison in food and water that were used to kill people.
Fear of spiders may also be cultural. For instance, people in South Africa have an extreme fear of spiders, while some people in Chile include spiders in their diet.
Symptoms include palpitations, trembling, and extreme anxiety when they find spiders in their surroundings, or even see spiders on TV or pictures in books. They would try to avoid places where they know they would find spiders and would wear protective clothing when they go outdoors.
Treatment includes desensitization therapy where they are taught that not all spiders are harmful. Anti-anxiety medications may be given if this fear renders a person dysfunctional.