Also known as Toxicodendron radicans, poison ivy is native to North America.
It mainly grows on the edges of woodland where there is plenty of sunlight. It is a low plant, a shrub. It may have green berries, and green-yellow flowers grow in spring.
The plant is known for its clusters of three leaflets, ranging in color from light to dark green. Each leaf grows on its own stem, and it is connected to a main vine. There are no thorns.
Poison ivy is not a true ivy but tends to climb telephone poles and trees. It is a member of the cashew family.
"Leaflets three, let it be" and "Hairy vine, no friend of mine" are two common mnemonic rhymes to describe the appearance of poison ivy.
According to the American Academy of Dermatology (AAD), 85 percent of the population in the United States is allergic to poison ivy. If these people touch the plant, they will develop a rash.
The remaining 15 percent of the population have no reaction, but even those who are not normally allergic should take care, as the chance of a reaction increases with age and with repeated exposure.
What's poisonous about poison ivy?
Poison ivy: "Leaflets three; let it be."
Poison ivy sap is found in nearly every part of the plant, including the leaves, stems, and roots. The sap contains an oil called urushiol, a pale-yellow, oily substance.
If any of this extremely sticky oil touches the skin, it can cause a blistering skin rash.
Urushiol is also found in poison oak and poison sumac.
A reaction to urushiol can happen when there is direct contact from touching contaminated objects, such as shoes after walking, and from breathing in smoke from burning poison ivy.
The most dangerous type of exposure is when a person inhales the smoke as the plant is burned.
When a person is exposed to poison ivy, a rash can appear between 12 and 72 hours after exposure. The more allergic to poison ivy you are, the faster it will appear.
Signs of a reaction to poison ivy include:
- intense itching
- red skin or red streaks
- red bumps, called papules
- blisters, often developing in lines and oozing
- crusting skin
The rash is not contagious and it does not spread. If it appears to be spreading, this is because of a delayed reaction.
It can take several weeks for the rash to heal.
When to see a doctor
If an individual develops any of the following signs or symptoms, it is important to seek immediate medical attention:
- trouble breathing
- difficulty swallowing
- swollen tongue
- a rash covering the face, the genitals, or most of the body
- swelling eyelids, to the point that the eyes close
A serious allergic reaction can occur in the nasal passages, throat, and lungs. They may have difficulty breathing. Urgent medical care is needed if someone stops breathing.
If the person has an Epipen, a bystander can help them to use it.
A poison ivy rash will generally clear up on its own within 2 to 3 weeks. No specific medical treatments are available on prescription.
Eyelids may swell as a reaction to poison ivy.
However, the following may offer some relief:
Removing clothes and showering when comig in from outside. Rinsing the skin with cool, soapy water might help remove the urushiol if it is done within one hour of contact with the plant.
Soaking in cool water to ease burning and itching, but not warm or hot water, as this can make the reaction worse. A cool oatmeal bath may help.
Over-the-counter calamine and cortisone creams should reduce itching.
Oral antihistamine, such as Allegra (fexofenadine), Zyrtec, or Benadryl ease inflammation and itching. They are available over the counter.
Many of these drugs can cause drowsiness. The individual should not drive or operate machinery until they know how the drugs will affect them.
Topical diphenhydramine can reduce itching, but it can also cause an inflamed reaction of its own, making the area sore and red. This can happen some days after contact.
If the rash is particularly severe, with a large number of blisters, a doctor may prescribe an oral corticosteroid. Injectable corticosteroids are often given to prevent further progress of the reaction. If the rash becomes infected, an oral or topical antibiotic might be prescribed.
Taking oral antihistamines before bed may help the patient sleep better. The itch can be intense and interrupt sleep.
Patients should not scratch the rash or burst any blisters, as this can lead to infection.
Cool compresses may help to soothe the itch, made from a clean washcloth soaked in cold water.
Risk factors and prevention
People at the highest risk of a poison ivy reaction are those who are exposed to the plants.
This includes those who do a lot of outdoor hobbies or whose job requires them to work outdoors
Jobs that can expose a person to poison ivy include:
Individuals who work outside are most at risk from poison ivy.
- construction workers
Tips to reduce the risk include:
- learning to identify the plant in order to avoid it
- wearing long pants, socks, and gloves
- cleaning all clothing and shoes after being outdoors, if you might have come in contact with poison ivy
- washing the skin immediately with soap and water, then rinsing thoroughly
- using an OTC skin cream containing bentoquatam before going outdoors to an area with poison ivy, as this can block urishiol from affecting the skin
- cleaning pets thoroughly if they may have been in contact with poison ivy as they can carry urushiol on their skin and coat
Pets, too, can be sensitive to the toxin, so they should be kept away from poison ivy where possible.
Reaction can develop as you age with repeated exposure, so even if you are not allergic to poison ivy use gloves and care with handling. Poison ivy sap on your clothes or on the dog's fur can transfer to others.