Poison ivy (Eastern U.S.) or poison oak (Western U.S.) is a delayed allergic reaction.  Brushing the plant on the skin results in blisters and slightly elevated lesions 1-2 days after exposure, accompanying a severe itch. Poison ivy, or poison oak, typically has a linear pattern. This image displays poison ivy in linear lesions, due to the patient either rubbing the allergen across the skin or brushing up against the poison ivy plant. This image displays broad areas of inflammation with a linear pattern typical of poison ivy (Eastern U.S.) or poison oak (Western U.S.). This image displays the poison ivy allergen on the face.  This image displays a rash with a linear distribution typical of poison ivy.  This image displays fluid-filled blisters typical of the intense allergic reaction of poison ivy dermatitis. This image displays poison ivy dermatitis where the allergen touched the skin. Linear streaks with bumps or blisters are common in those with a poison ivy allergy who come in contact with the oil from the plant. This image displays poison ivy, which is identifiable by the grouping of three leaves. Also note: Berries carry the allergen as well. This image displays the poison oak plant, which, like poison ivy, has 3 leaves. Unlike poison ivy, however, the poison oak plant typically looks more like a shrub and has leaves that resemble an oak tree's leaves. Poison sumac has between 7 and 13 leaves on each branch of the plant. Poison sumac can be differentiated from nonpoisonous types of sumac by the location of the fruit on the plant, with the fruit of the poisonous plant growing between the leaf and the branch, opposed to the ends of the branches.
Share |

Poison Ivy, Oak, and Sumac  Information for adults

Picture of Poison Ivy, Oak, and Sumac: Poison ivy (Eastern U.S.) or poison oak (Western U.S.) is a delayed allergic reaction.  Brushing the plant on the skin results in blisters and slightly elevated lesions 1-2 days after exposure, accompanying a severe itch. Divider line
Poison ivy (Eastern U.S.) or poison oak (Western U.S.) is a delayed allergic reaction. Brushing the plant on the skin results in blisters and slightly elevated lesions 1-2 days after exposure, accompanying a severe itch.
left arrow
right arrow
Overview
Poison ivy, poison oak, or poison sumac dermatides are all reactions to the oil (called urushiol) found on the leaves, stems, and roots of poison ivy, poison oak, and poison sumac plants.
  • People typically have itchy bumps (papules) and blisters (vesicles).
  • Itching can be intense, and secondary bacterial infection can result from scratching.
  • Scratching does not spread lesions; the lesions with the most antigen appear first and then, as the immune response increases, lesions with less antigen begin to erupt.
  • Skin lesions usually begin to appear after 48 hours of initial exposure.
  • Symptoms are usually related to severe itching.
Who's At Risk
Poison ivy, poison oak, and poison sumac may affect people of all ages.
Signs and Symptoms
  • Poison ivy, poison oak, and poison sumac can occur anywhere on the body where the exposure to the plants has occurred.
  • Linear red and brown-red, raised areas and blisters are noted. Crusted lesions may be seen.
  • A "black dot variant" has been described. (The oil from the plant leaves a black dot on the skin.)
  • Extreme facial swelling (edema) may be seen if there is significant exposure to the face.
Self-Care Guidelines
  • It is important to use soap and water to wash all potentially exposed areas since the oil of the poison ivy, poison oak, and poison sumac plants adhere to the skin.
  • Once the oil has been washed off, there is no risk of spreading poison ivy, poison oak, or poison sumac to other parts of the body.
  • Be sure to wash any garments potentially exposed to the oil as well.
  • Soothing oatmeal baths (such as Aveeno® Skin Relief Bath Treatment) and calamine lotion may be helpful in relieving symptoms.
  • Wear protective clothing (eg, pants and long-sleeved shirts) and barrier cream (Ivy Block™) applied 15 minutes before potential exposure to avoid future reactions.
When to Seek Medical Care
Seek medical evaluation for a rash that does not respond to self-care measures or appears to be flaring or worsening.
Treatments Your Physician May Prescribe
Your physician may prescribe:
  • In severe cases involving large body areas, a 14–20 day course of oral steroids (prednisone).
  • In cases with more limited skin involvement, medium- to high-potency topical steroids may be used to treat the trunk and extremities, while low-potency topical steroids may be prescribed to treat the face and skin fold areas.
  • Oral antihistamines may be prescribed for itching.
  • Topical or oral antibiotics may be needed if an infection is suspected.

References

Bolognia, Jean L., ed. Dermatology, pp.227-229. New York: Mosby, 2003.

Freedberg, Irwin M., ed. Fitzpatrick's Dermatology in General Medicine. 6th ed, pp.1167-1168. New York: McGraw-Hill, 2003.
Last Updated: 22 Dec 2008