Poison Ivy Rash

 It is usually not hard to identify a child with a poison ivy rash, especially a classic case of poison ivy, which might include a child with a known exposure to poison ivy after a camping trip, hike in the woods, or day at the lake, who then develops a red, itchy rash all over his body a few days later.
After exposure to the leaves, stems, or roots of a poison ivy plant, children develop symptoms of poison ivy within 8 hours to a week or so, including:

• an intensely itchy rash
• red bumps that often are in a straight line or streaks, from where the poison ivy plant had contact with your child's skin
• vesicles and blisters that are filled with fluid

Keep in mind that children exposed to poison sumac and poison oak, other members of the genus Rhus or Toxicodendron, can get these same symptoms that are generically referred to as poison ivy symptoms above. (Using medical terminology, these children develop rhus dermatitis or allergic contact dermatitis, an intensely pruritic, linear, erythematous, papulovesicular rash after exposure to the urushiol oil in poison ivy.)
Other characteristic signs and symptoms of poison ivy are that the rash will worsen over days or weeks without treatment with steroids, the rash may not go away for up to three weeks without treatment, many children will have worsening symptoms with each exposure, and that some areas of a child's skin that had less exposure to the poison ivy plant will get the rash later than others.

This article is taken from- http://pediatrics.about.com/od/poisonivy/a/06_psn_ivy_rash.htm