However, do not assume that you are one of the few people who are not sensitive. Only about 15 percent of people seem to be resistant. Sensitivity to poison ivy tends to decline with age. Children who have reacted to poison ivy will probably find that their sensitivity decreases by half by young adulthood without repeated exposure. People who were once allergic to poison ivy may even lose their sensitivity later in life.
Some people are very sensitive to poison ivy.
They can develop a severe rash with blisters and extreme swelling on their face, arms, legs and genitals. Such severe cases need medical treatment. Poison sumac, however, has a row of paired leaflets. On each of these plants, the middle or end leaflet is on a longer stalk than the other two or more leaflets. This differs from many other look-alikes.