noun, plural: glochids
Any of the hair-like spine or bristle often with a barbed tip on cactus
Glochids (or glochidia, singular: glochidium) are hair-like spines or bristles found on the cactus body, particularly of those in the subfamily Opuntioideae. Opuntioideae is a subfamily of the family Cactaceae and exemplified by Opuntia (prickly pear) and cholla.
Glochids arise from the areoles. Areoles are bumps on the body of the cactus. Most glochids are barbed. And a simple touch would easily detach the glochids from the cactus body. The glochids lodge in the skin and because of the barbs removing them on skin may be difficult. It may cause dermatitis that could persist for months, especially without treatments. Glochids that come in contact to the skin may cause skin irritation. Thus, they are essential to the cactus for their protective role.
The prickly pear cactus, endemic to Central America, is sometimes used as an ornamental plant and also cultivated for its edible fruit. Care should be taken into account since its fruit also bears glochids. As such, consumption of this fruit may affect the hard palate and the oral mucosa. The lesion may resemble scabies and is referred to as sabra dermatitis.1
1 Modi, G. M., Doherty, C. B., Katta, R., and Orengo, I. F. (2009). Irritant Contact Dermatitis from Plants. Dermatitis 20(2):63-78. Retrieved from ://www.medscape.com/viewarticle/706404-2.