She makes a "poultice" out of seaweed. Here is the modern definition of poultice from http://www.merriam-webster.com/dictionary/poultice : a soft usually heated and sometimes medicated mass spread on cloth and applied to sores or other lesions. Today's usage of the word is used to indicate a cloth compress with medicine on it that is used to relieve pain from an injury, and this is exactly how Juana uses it--she uses seaweed though instead of a cloth. Seaweed is STILL thought to have medicinal properties and it is STILL used to heal wounds, improve skin quality and relieve aches and pains! In fact, there are websites where you can order poultices made of seaweed! So, Juana used seaweed because she could not afford the expensive treatment from the doctor, but little did she know she was using a remedy that now wealthy people seek out to fix what ails them!
In the book The Pearl by John Steinbeck Juana and Kino live a simple existence. They have each other and a loving baby boy whom they sit gently in a homemade hanging box to catch some sunshine after the baby's bath. Kino is watching his baby smiling and he spots a scorpion climbing down the side of the chord towards the baby. Before he can catch the scorpion it stings his son. Kino then grabs it up and squashes it in anger.
Kino's wife Juana pulled the baby out of the box and sucked the wound trying to suck out any poison. They took the child to the doctor but he had refused to see the child and had his servant tell the two that he was out.
"She gathered some seaweed and made a flat damp poltice of it, and this she applied to the baby's swollen shoulder." (15)
Juana applied a poultice of brown seaweed.