Pica pica (Mucuna pruriens) is one of the plants in Puerto Rico that can cause a lot of discomfort during the winter months. Its vines can grow to 50 feet in length and grow what some call velvet beans or in Nigeria they call them Devil Beans.  Pica pica means itch or burn so there is a double meaning there.

Pica pica velvet beans

I’ve heard all kinds of stories about what causes the itching. Some think it is like poison ivy or carrasco and that it is Urushiol that causes it. That turns out to not be true. I found a study of mucuna pruriens and apparently the fuzzy coating on the beans is the source.  These hairs that grow on the beans are trichomes or spicules that they call cowhage.

I have found that removal of these tiny hairs is the only way to relieve the itch.  I use tape, put it over the affected area then remove the tape.  I guess it works kind of like a lint brush.  We’ve tried baby powder, rubbing alcohol, showers, etc but to really get relief those hairs have to be taken out.

The plant itself is best to just clip before they flower and have the bean pods.  The vines grow out of the ground, you can handle them and just pull the roots out, no problem.  Just be careful of any mature bean pods, stay away from those.  Fairly simple but if you don’t watch out for it they can take over!

They tend to grow in areas that have been recently cleared.

Pica pica Vine / Leaves

During the dry season people will set hillsides on fire to try and eradicate it before the wind spreads the tiny hairs all over the place.  If you leave your laundry out on a line to dry, like many do, you will get the itch when you lie in bed or use your towels!  Picapica!!