Disease: Poison Ivy, Oak, and Sumac

Poison ivy, oak, and sumac facts

  • Poison ivy, poison oak, and poison sumac are plants than can cause an itchy rash upon contact.
  • A substance called urushiol, found in these plants, causes the rash.
  • The rash is not contagious.
  • The rash usually disappears in one to three weeks.
  • The majority of cases can be treated at home.

What are poison ivy, poison oak, and poison sumac?

Poison ivy, poison oak, and poison sumac are plants that can cause a rash if individuals come in contact with the oily resin found in them.

Poison ivy (Toxicodendron radicans -- eastern poison ivy/Toxicodendron rydbergii -- western poison ivy) typically grows as a vine or shrub, and it can be found throughout much of North America (except in the desert, Alaska, and Hawaii). It grows in open fields, wooded areas, on the roadside, and along riverbanks. It can also be found in urban areas, such as parks or backyards. Poison ivy plants typically have leaf arrangements that are clustered in groups of three leaflets, though this can vary. The color and shape of the leaves may also vary depending upon the exact species, the local environment, and the time of year. The plant may have yellow or green flowers, and white to green-yellow berries, depending on the season.

Picture of poison ivy

Poison oak (Toxicodendron diversilobum) grows as a vine or shrub, and it is found in the western United States and British Columbia. It also has a leaf arrangement similar to poison ivy, with clusters of three leaflets. The leaves may sometimes resemble true oak leaves.

Picture of poison oak

Poison sumac (Toxicodendron vernix) grows as a shrub or small tree, and it is found in the eastern/southeastern United States. It grows in very wet areas, and it can be found along the banks of the Mississippi River. Each stem contains seven to 13 leaves arranged in pairs. It has the potential to cause a more severe rash than either poison ivy or poison oak.

Picture of poison sumac

What causes a poison ivy, oak, or sumac rash?

Exposure to all of these plants can produce a rash, which is caused by sensitivity to an oily resin found in these plants called urushiol. This substance can be found on the leaves, stems, flowers, and roots of these plants. Interestingly, it can remain active even after the plant has died. Exposure to even very small amounts of urushiol, amounts less than a grain of table salt, will lead to the development of a rash in 80%-90% of individuals.

The rash (an allergic contact dermatitis) can be caused by direct contact with urushiol by touching the plants or by indirect contact with the plant oil that may have contaminated a pet's fur, tools, clothing, or other surfaces. Airborne contact is also possible if these plants are burned and the urushiol particles land on the skin, and it can affect the lungs as well if the urushiol is inhaled. In the United States, Toxicodendron dermatitis is the most common cause of contact dermatitis.

Sensitivity to urushiol occurs when individuals come into contact with it. The first time a person is exposed, they may not develop a rash. However, with repeated exposure, sensitivity develops that ultimately leads to the development of the characteristic rash. Most people (about 85%) will develop sensitivity, while a small percentage of individuals (about 15%) never develop an allergic reaction to urushiol.

What are risk factors for poison ivy, oak, or sumac rash?

Any individual who comes into contact with these plants is at risk for developing the rash. However, people who spend more time outdoors in geographic areas where these plants are known to grow are at higher risk. This may include certain occupations associated with outdoor work in these areas, such as gardeners, groundskeepers, farmers, forestry workers, and construction workers. Hiking enthusiasts may also be at higher risk if they venture into areas where these plants are present.

What are symptoms and signs of a poison ivy, oak, or sumac rash?

Susceptible people will develop the characteristic rash after exposure to the urushiol from these plants, typically within 12-72 hours after the initial contact. The signs and symptoms can include the following:

  • Redness of the skin
  • Swelling of the skin
  • Itching of the skin
  • An outbreak of small or large blisters

The rash may appear bumpy, streaky, linear or patchy, and it will affect the areas that have come into contact with the oil resin. Areas that have been exposed to a larger amount of urushiol may develop the rash more quickly, and the rash may appear more severe. In some instances, new lesions may continue to appear for up to two to three weeks. One can spread the rash to other parts of the body if one's contaminated hands (with the oil resin) touch other areas. The fluid that sometimes oozes from the blisters does not contain urushiol and therefore does not spread the rash, and other individuals who touch this fluid will not develop the rash. In order to spread the rash to someone else, they must directly come into contact with the oil resin. Generally speaking, the rash slowly improves and disappears after one to three weeks in most individuals. Overall, the symptoms may range from mild to severe. Rarely, in extreme cases, an anaphylactic reaction can develop.

Picture of a poison oak rash; SOURCE: CDC

If these plants are burned, the airborne particles of urushiol can be inhaled, causing respiratory difficulty from irritation of the lungs. Occasionally, this reaction can be severe.

How do physicians diagnose poison ivy, oak, and sumac rashes?

The diagnosis of this rash is typically made by a health-care professional after obtaining a thorough history and performing a detailed exam of the skin. While some individuals will know and report exposure to poison ivy, oak, or sumac, others may not be aware of it and may not recall any exposure. The appearance of the characteristic rash is usually all that is needed to make the diagnosis. No blood tests or imaging studies are necessary.

What is the treatment for a poison ivy, oak, or sumac rash?

The initial treatment for someone who has recently been exposed to any of these plants includes rinsing the affected area with copious amounts of warm water within 20-30 minutes of exposure to remove the oily plant resin. The effectiveness of rinsing decreases with the passage of time, as the oily plant resin is quickly absorbed into the skin. Some authorities recommend rinsing with rubbing alcohol, commercially available poisonous plant washes, or degreasing soaps and detergents. It is also important to scrub under the fingernails to remove any remnants of the plant resin. In addition, thoroughly clean clothing or any objects that may have come into contact with these plants.

Picture of poison ivy plant and poison ivy skin rash

If the characteristic rash develops, initial treatment consists of symptomatic care, as in most cases, the rash will improve on its own after one to three weeks. Self-care at home is usually all that is necessary. In the meantime, the following treatments may be useful to alleviate symptoms:

  • Apply cool compresses to the skin.
  • Use topical treatments to relieve itching, including calamine lotion, oatmeal baths, or aluminum acetate (Domeboro solution).
  • Oral antihistamines, such as diphenhydramine (Benadryl), can also help relieve itching.
  • For a more severe rash, a health-care professional may prescribe a high-potency steroid cream or an oral corticosteroid (such as prednisone).
  • Over-the-counter pain medication may be necessary for pain control.
  • Antibiotics may be prescribed if the rash becomes infected. Avoid scratching the rash to prevent the development of a bacterial infection.
  • Go to the nearest emergency department or call an ambulance if experiencing an anaphylactic reaction (severe allergic reaction) characterized by difficulty breathing, difficulty swallowing, facial swelling, or if one is exposed and have had a previous severe reaction to these plants. Also seek medical care if the rash involves the genitals or the face or if the rash shows signs of infection.

What causes a poison ivy, oak, or sumac rash?

Exposure to all of these plants can produce a rash, which is caused by sensitivity to an oily resin found in these plants called urushiol. This substance can be found on the leaves, stems, flowers, and roots of these plants. Interestingly, it can remain active even after the plant has died. Exposure to even very small amounts of urushiol, amounts less than a grain of table salt, will lead to the development of a rash in 80%-90% of individuals.

The rash (an allergic contact dermatitis) can be caused by direct contact with urushiol by touching the plants or by indirect contact with the plant oil that may have contaminated a pet's fur, tools, clothing, or other surfaces. Airborne contact is also possible if these plants are burned and the urushiol particles land on the skin, and it can affect the lungs as well if the urushiol is inhaled. In the United States, Toxicodendron dermatitis is the most common cause of contact dermatitis.

Sensitivity to urushiol occurs when individuals come into contact with it. The first time a person is exposed, they may not develop a rash. However, with repeated exposure, sensitivity develops that ultimately leads to the development of the characteristic rash. Most people (about 85%) will develop sensitivity, while a small percentage of individuals (about 15%) never develop an allergic reaction to urushiol.

What are risk factors for poison ivy, oak, or sumac rash?

Any individual who comes into contact with these plants is at risk for developing the rash. However, people who spend more time outdoors in geographic areas where these plants are known to grow are at higher risk. This may include certain occupations associated with outdoor work in these areas, such as gardeners, groundskeepers, farmers, forestry workers, and construction workers. Hiking enthusiasts may also be at higher risk if they venture into areas where these plants are present.

What are symptoms and signs of a poison ivy, oak, or sumac rash?

Susceptible people will develop the characteristic rash after exposure to the urushiol from these plants, typically within 12-72 hours after the initial contact. The signs and symptoms can include the following:

  • Redness of the skin
  • Swelling of the skin
  • Itching of the skin
  • An outbreak of small or large blisters

The rash may appear bumpy, streaky, linear or patchy, and it will affect the areas that have come into contact with the oil resin. Areas that have been exposed to a larger amount of urushiol may develop the rash more quickly, and the rash may appear more severe. In some instances, new lesions may continue to appear for up to two to three weeks. One can spread the rash to other parts of the body if one's contaminated hands (with the oil resin) touch other areas. The fluid that sometimes oozes from the blisters does not contain urushiol and therefore does not spread the rash, and other individuals who touch this fluid will not develop the rash. In order to spread the rash to someone else, they must directly come into contact with the oil resin. Generally speaking, the rash slowly improves and disappears after one to three weeks in most individuals. Overall, the symptoms may range from mild to severe. Rarely, in extreme cases, an anaphylactic reaction can develop.

Picture of a poison oak rash; SOURCE: CDC

If these plants are burned, the airborne particles of urushiol can be inhaled, causing respiratory difficulty from irritation of the lungs. Occasionally, this reaction can be severe.

How do physicians diagnose poison ivy, oak, and sumac rashes?

The diagnosis of this rash is typically made by a health-care professional after obtaining a thorough history and performing a detailed exam of the skin. While some individuals will know and report exposure to poison ivy, oak, or sumac, others may not be aware of it and may not recall any exposure. The appearance of the characteristic rash is usually all that is needed to make the diagnosis. No blood tests or imaging studies are necessary.

What is the treatment for a poison ivy, oak, or sumac rash?

The initial treatment for someone who has recently been exposed to any of these plants includes rinsing the affected area with copious amounts of warm water within 20-30 minutes of exposure to remove the oily plant resin. The effectiveness of rinsing decreases with the passage of time, as the oily plant resin is quickly absorbed into the skin. Some authorities recommend rinsing with rubbing alcohol, commercially available poisonous plant washes, or degreasing soaps and detergents. It is also important to scrub under the fingernails to remove any remnants of the plant resin. In addition, thoroughly clean clothing or any objects that may have come into contact with these plants.

Picture of poison ivy plant and poison ivy skin rash

If the characteristic rash develops, initial treatment consists of symptomatic care, as in most cases, the rash will improve on its own after one to three weeks. Self-care at home is usually all that is necessary. In the meantime, the following treatments may be useful to alleviate symptoms:

  • Apply cool compresses to the skin.
  • Use topical treatments to relieve itching, including calamine lotion, oatmeal baths, or aluminum acetate (Domeboro solution).
  • Oral antihistamines, such as diphenhydramine (Benadryl), can also help relieve itching.
  • For a more severe rash, a health-care professional may prescribe a high-potency steroid cream or an oral corticosteroid (such as prednisone).
  • Over-the-counter pain medication may be necessary for pain control.
  • Antibiotics may be prescribed if the rash becomes infected. Avoid scratching the rash to prevent the development of a bacterial infection.
  • Go to the nearest emergency department or call an ambulance if experiencing an anaphylactic reaction (severe allergic reaction) characterized by difficulty breathing, difficulty swallowing, facial swelling, or if one is exposed and have had a previous severe reaction to these plants. Also seek medical care if the rash involves the genitals or the face or if the rash shows signs of infection.

Source: http://www.rxlist.com

The initial treatment for someone who has recently been exposed to any of these plants includes rinsing the affected area with copious amounts of warm water within 20-30 minutes of exposure to remove the oily plant resin. The effectiveness of rinsing decreases with the passage of time, as the oily plant resin is quickly absorbed into the skin. Some authorities recommend rinsing with rubbing alcohol, commercially available poisonous plant washes, or degreasing soaps and detergents. It is also important to scrub under the fingernails to remove any remnants of the plant resin. In addition, thoroughly clean clothing or any objects that may have come into contact with these plants.

Source: http://www.rxlist.com

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