Poison ivy rash can be recognized by its characteristic swath of tiny red blisters at the site of contact. The blisters coalesce to form a lesion shaped like the initial line of contact with the toxic foliage. Urushiol oil from any part of the poison ivy plant, whether the plant is growing, in bloom, dead, or dormant, will seep through clothing and engender the pus-filled bumps that are indicative of the body trying to fight toxins. For up to three days after contact with the oil from a poison ivy plant, a person might see the rash spreading as leftover oil spreads to surrounding skin or transfers to new locations through residue on clothing, boots or gloves. Inflammation and itching generally precede the growth of blisters, arising within 15 minutes of contact, while the onset of blisters is generally not immediate, taking between one to three days to occur.
Determining whether a person has had immediate exposure to wooded areas that may contain poison ivy is the first step in recognizing whether a rash of blisters is linked to poison ivy. One can also consider whether a person has handled tools or clothing that has been in a wooded area in the last several days and could contain residue from poison ivy foliage. A recent experience near smoke from burning foliage can also signal the rash is linked to poison ivy. If none of these conditions exists, the rash could be ringworm, spider bites, or erythema migrans, which are often mistaken for a poison ivy rash.
Scientific reports state that all people are generally born with initial and fleeting immunity to the poison ivy rash. While the toxic resin from poison ivy affects nearly all children and adults, some studies state that a few people might retain immunity through adulthood. Repeated exposure will eventually break down anyone’s immunity, botanists warn.
The length of time the rash remains can also help one recognize poison ivy. Unlike some other rashes that may only last a week, a poison ivy rash can last between 12 and 30 days. Longevity of infection is typically caused by reintroduced poison ivy resin to the skin via leftover oils under nails or on other objects. Toxic oils from poison ivy can be translocated from objects for up to one year.
After the initial inflammation, the appearance of a poison ivy rash may shift from blisters to open sores oozing pus. If this condition is recognized, doctors recommend emergency treatment since pus from the blisters can seep into the skin and get into the bloodstream, causing blood poisoning. Other emergency states of poison ivy rash include blisters on the genitals, eyes, and mouth. Poison ivy rash in other locations on the skin can be treated at home using zinc oxide, antihistamine, sodium bicarbonate or calamine lotion.