Number sign. Not to be confused with the Chinese character äº, the sharp sign (â¯), the viewdata square (â), the numero sign (â), the equal and parallel to symbol (â) or the game Tic-tac-toe's grid. The symbol # is most commonly known as the number sign, hash, or pound sign.
The poison ivy rash is not contagious. When a person touches the poison ivy leaf, a substance on the surface of the leaf (a resin) rubs off. Over the next 48 to 72 hours the skin reacts to the resin by becoming red and developing bumps and blisters at and around the site where the resin was.
In fact, allergic contact dermitis is so widespread that many of the species have a common name that starts with poison, including poison oak (Toxicodendron diversilobum) and poison sumac (Toxicodendron vernix). One way to tell the difference between poison oak and poison sumac is to consider the location.