The Call-On-Doc Guide for Poison Ivy, Sumac, and Oak

Published on Jun 20, 2023 | 4:09 PM

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Found in many parts of the United States, poison ivy, poison oak, and poison sumac are some of the many year-round hazards to be aware of when enjoying time outdoors. Affecting tens of millions of Americans each year with a rash, wildlife centers, camps, and parks often make an effort to educate visitors through signs and classes. While most cases will only result in a rash upon contact, around 10% to 15% of people are considered extremely allergic to the plants (1).

Varying slightly based on the region, poison ivy, sumac, and oak each have a relatively similar appearance throughout the United States, Canada, and parts of Mexico. It's thus important to be able to identify them. 

Identifying poison ivy

Poison ivy can be found throughout North America, including the United States and Canada. It typically grows in wooded areas, along roadsides, in fields, and even in urban environments.

Identifying poison ivy involves looking for specific characteristics. It is a deciduous plant or a plant that sheds its leaves seasonally with compound leaves that consist of three leaflets. The leaflets are usually smooth-edged, but they can be slightly toothed or lobed. The leaves are shiny, and their color can range from green in spring and summer to red or yellow in the fall. Additionally, the plant may have green or white berries and can grow as a low-ground cover, a climbing vine, or an upright shrub. 


Identifying poison sumac

Poison sumac is primarily found in wetlands and swampy areas of the eastern and southeastern regions of North America, including parts of the United States and Canada. It prefers a more humid and waterlogged habitat compared to poison ivy and poison oak.

Identifying poison sumac involves looking for certain distinguishing features. It is a woody shrub or small tree with compound leaves composed of multiple leaflets arranged in pairs. Each leaf typically consists of 7 to 13 leaflets, with one leaflet at the tip. The leaflets have smooth edges and are elongated, oval, or oblong in shape, tapering at the ends. Unlike poison ivy, poison sumac has leaves that are shiny on both sides. The plant also produces clusters of small greenish-yellow or cream-colored berries. 


Identifying poison oak

Poison oak is primarily found in North America, particularly in regions such as the United States, Canada, and Mexico. It is most prevalent in the western and southern parts of the United States, including the Pacific Coast, the Southwest, and the Southeast.

Identifying poison oak involves looking for specific characteristics. It is a shrub or vine that can grow low to the ground or climb on trees or structures. The leaves of poison oak resemble those of an oak tree, with each leaf typically consisting of three leaflets. The leaflets are smooth-edged, but they can be slightly lobed or toothed. The leaves are green in the spring and summer and often turn red or yellow in the fall. Like poison ivy, poison oak also produces green or white berries. 


How does poison ivy rash develop?

Coincidentally sharing the same family of trees as mangos and cashews, poison ivy, sumac, and oak are all part of the Anacardiaceae family. One similarity between them is the production of urushiol oil, a substance that causes allergic contact dermatitis in almost all people. (2) While mangos and cashews are generally sold in such a way that the oil is removed or in amounts too small to be effective, the latter three plants naturally produce enough to cause a reaction just by touching any part of them alone. The reaction in itself is an irritating rash that develops after some time and goes away on its own, but the following process is important to understand so you know what to watch out for:

  1. The immune system recognizes the allergen as foreign and develops an immune response 
  2. Upon subsequent exposure, the sensitized immune system recognizes the allergen and triggers an immune reaction, releasing inflammatory chemicals that cause redness, swelling, and itching 
  3. When your immune cells are then infiltrated, the inflammation will worsen, causing allergic contact dermatitis. This stage can be characterized by blisters filled with liquid. 
  4. Over a short period of time, the blisters will break, release the liquid, and then crust over as the body’s healing process has already begun. 

The severity of the reaction can vary, but further contact with poison ivy, oak, or sumac will cause the rash to be present in a greater or separate area of the body. (3)

How do doctors diagnose poison ivy?

Doctors can determine a rash from poison ivy, oak, or sumac by looking at it and having a brief conversation with the patient. Most often, medical professionals will get an indication that the patient has gone to an area where any of the three plants are present. (4) While the rash can sometimes be confused for shingles, visual confirmation that the rash is isolated to where the plant or urushiol made contact with the skin.

How do you tell if it's poison ivy or poison oak?

Poison ivy, oak, and sumac cause the same rash due to each producing the same substance that causes the allergic reaction. 

How long does it take for poison ivy, oak, and sumac to go away?

The duration of a rash caused by poison ivy, poison oak, or poison sumac can vary from person to person and depends on several factors, including the individual's sensitivity, the extent of exposure, and how the rash is managed. On average, the rash typically takes about 1 to 3 weeks to resolve, but it can sometimes last longer. Here are the stages of poison ivy and poison oak rashes:

  1. Early stages: Within a few hours to a few days after exposure, the first signs of a rash may appear, such as redness, itching, and swelling.
  2. Rash progression: The rash usually develops and worsens over the next few days. Blisters may form, and the itching can become more intense.
  3. Healing process: Over the course of 1 to 3 weeks, the rash gradually starts to improve. The blisters may dry up and crust over, and the skin begins to heal. It is crucial to avoid scratching or picking at the rash to prevent infection.
  4. Residual effects: Some individuals may experience residual effects such as dryness, flaking, or discoloration of the skin even after the rash has resolved. These effects usually fade with time.

During the phases where symptoms like itching and general discomfort are a problem, patients can purchase topical creams and oral antihistamines to treat themselves. If needing a prescription, Call-On-Doc offers more effective products like the topical antibiotic mupirocin as well as the oral medications cephalexin and doxycycline. 

How do you stop poison ivy before it starts?

Learn to identify poison ivy: Familiarize yourself with the appearance of poison ivy plants, including their leaves, stems, and growth habits. Remember the phrase "Leaves of three, let it be" to help in identification.

  • Avoid contact: When you're in areas where poison ivy may be present, such as forests, fields, or overgrown areas, try to stay on cleared paths or trails. Avoid touching or brushing against any plants that resemble poison ivy.
  • Wear protective clothing: If you anticipate being in an area with potential poison ivy exposure, wear long sleeves, long pants, socks, and closed-toe shoes. Consider tucking your pants into your socks to minimize contact with your skin. Wearing gloves can also provide additional protection.
  • Apply a barrier cream: Applying a barrier cream or lotion containing bentoquatam (such as IvyBlock) can create a protective layer on your skin, reducing the chances of urushiol oil from poison ivy penetrating the skin.
  • Wash your skin and clothing: After being in potential contact with poison ivy, wash your skin thoroughly with soap and water as soon as possible. Be sure to clean under your nails and any other areas that may have come into contact with the plant. Also, wash your clothing and any items that may have been exposed to urushiol.
  • Be cautious with pets and tools: Remember that pets can potentially carry urushiol oil on their fur, so avoid touching them without taking proper precautions. If you're working in areas with potential poison ivy, use gloves and tools to minimize contact.

While these steps can reduce the risk, it's important to note that even indirect contact with urushiol oil, such as through contaminated objects or airborne particles from burning plants, can still cause a reaction. If you suspect you have come into contact with poison ivy, taking prompt measures to wash your skin and clothing can help minimize the chances of developing a rash. For more tips on poison ivy, check out this video from a Call-On-Doc Board-Certified Dermatologist.

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Wayne C. Hahne,

English graduate and Call-On-Doc’s medical resource guide, Wayne C. Hahne is an experienced and passionate medical education content expert. Through diligent research, provider interviews and utilizing the industry's leading resources for wellness information, it is Mr. Hahne’s personal mission to educate the general public on medical conditions with in-depth and easy-to-understand written guides.

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