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.
Poison Ivy, Sumac and Oak. About 85 percent of the population is allergic to poison ivy, poison sumac or poison oak, and about 10 to 15 percent are extremely allergic. This is the most common allergic reaction in the U.S., and affects as many as 50 million Americans each year.