Urticaria Caused by Tarantula Hairs

Bites by spiders of the family Theraphosidae in humans and canines

“…Bites appear to cause only minor effects (Lucas et al, 1994;Isbister et al, 2001;Lim and Davie, 1970), based on the lack of case reports of severe effects in the literature. However, the hairs (setae) of South American theraphosid spiders have been responsible for urticating skin reactions and ocular injuries (Cooke et al, 1973;Blaikie et al, 1997;Castro et al, 1995;de Haro and Jouglard, 1998;Traub et al, 2001), that can cause more severe effects.…”

Invertebrates

“…Each urticating hair is covered by hundreds of small hooks and can cause severe itching when it makes contact with the skin. 33 Cooke et al 2 have shown that these hairs can embed themselves to a depth of 2 mm in human skin. A severe skin reaction has been observed by the authors in a colleague working with the Theraphosa blondi colony at the Louisiana State University School of Veterinary Medicine.…”

“…Individual spiders may have more than 1 million urticating hairs on their abdomen, at a density of approximately 10,000 hairs per square millimeter. 2 The urticating hairs are replaced after each successive molt.…”

Acute conjunctivitis and corneal foreign bodies secondary to tarantula hairs

“…2 There are four types of urticating hairs in tarantulas, categorized by the pattern of barbs. 3 A species can have more than one type. However, type III hairs are the most clinically significant, because they are able to penetrate the cornea deeply and cause irritation.…”