Scottish researchers, writing in the British Medical Journal, reported the cases of three people who suffered eye damage from touching the creatures.
Andrew J. Blaikie, of Ninewells Hospital in Dundee, wrote: "Tarantulas are becoming increasingly popular as pets. They are widely available, easily maintained and considered harmless as many are non-venomous. Unfortunately the popular American varieties that are less venomous have evolved highly urticarious [stinging] hairs to leave on their webs and flick at predators."
The report said all three patients went to their doctors complaining of itchy, gritty, red eyes.
"The hairs seemed to be migrating relentlessly through the media of the eye," causing cataracts, blurred vision and other problems, it added.