Poison ivy rash: Causes, treatment, and prevention

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Poison ivy is a plant that can cause severe skin inflammation or contact dermatitis. The plant contains a sap that causes delayed irritation upon skin contact.

Poison ivy, also known as Toxicodendron radicans, is native to North America and belongs to the cashew nut family.

It grows mainly on the forest edges in areas with lots of sunlight. Poison ivy is a shrub so it is generally short in height. It can produce green berries, and green-yellow flowers usually grow in spring.

People can recognize the plant by its compound leaves, which consist of three leaflets and range from light to dark green. Each leaf grows on its own stem and connects to the main vine. There are no thorns. Poison ivy isn’t a true ivy, but it does tend to climb telephone poles and trees.

“Leaflet three, leave it” and “Hairy Vine, Not a Friend of mine” are two common mnemonic rhymes that people use to identify poison ivy.

According to the American Academy of Dermatology, 85% of the US population are allergic to poison ivy. If these people touch the plant, they will develop a rash.

The remaining 15% may not respond to poison ivy. But even those who have never reacted to it should be careful, as repeated exposure to the plant can increase the likelihood of a reaction.

Share on PinterestPoison ivy contains urushiol, an oil that can cause a rash on human skin.

Poison ivy sap is present in almost every part of the plant, including the leaves, stems, and roots.

The juice contains an oil called urushiol, a pale yellow, sticky, oily substance that is also found in poison oak and poison sumac.

If any of these oils touch the skin, a blistered rash may develop.

A person may react to urushiol after:

  • touch the plant
  • Touching contaminated objects such as shoes that have come into contact with the plant
  • Inhaling smoke from burning poison ivy

The most dangerous type of exposure is when a person inhales the smoke from a burning plant.

Nettle can cause a reaction, but it can also be useful. Find out more about this plant here.

The rash usually appears within 3 days of exposure to the oil, but the time frame can vary significantly. The more sensitive a person is to poisoning ivy, the faster the rash can appear.

Signs of a reaction are:

  • severe itching
  • red skin or red streaks
  • red bumps called papules
  • swelling
  • Blisters, which often develop in lines and ooze
  • crusty skin

The rash is not contagious and does not spread to other areas of the body. If it seems to spread, it is due to a delayed response or further contact with contaminated objects.

It can take several weeks for the rash to heal.

When to see a doctor

If any of the following signs or symptoms occur, a person should see a doctor right away:

  • Difficulty breathing
  • difficulties swallowing
  • a swollen tongue
  • A rash that covers the face, genitals, or most of the body
  • swollen eyelids as far as the eyes close

A serious allergic reaction can occur in the nasal passages, throat, and lungs, making breathing difficult. A person with difficulty breathing needs immediate medical attention.

A poison ivy rash usually goes away within 2-3 weeks without treatment. There are several prescription treatments available and there are general treatment options.

People can also relieve symptoms with the following tips:

Take off clothes and shower when come in from the outside. If you only rinse the skin with water within 1 hour of contact with the plant, the urushiol can be removed. However, it is best to wash as soon as possible. If a person waits 10 minutes after washing, only about 50% of the urushiol is released. Over time, it becomes increasingly unlikely that a person will be able to wash off this substance.

Soak in cold water to relieve the burning sensation and itching, but avoid warm or hot water. A cool oatmeal bath can help.

Make cool compresses by soaking a clean washcloth in cold water. These can help soothe itchy skin.

Apply calamine and cortisone creams to reduce itching. These are available without a prescription.

Oral antihistaminesB. Fexofenadine (Allegra), Cetirizine (Zyrtec) or Diphenhydramine (Benadryl) can relieve inflammation and itching and are available without a prescription.

Zyrtec and Benadryl can both cause drowsiness. Hence, people should avoid taking it during the day when they need to be awake and alert. Taking oral antihistamines before bed can help the person sleep better as the itching can be intense and interrupt sleep.

Oral corticosteroids may be necessary if the person has a severe rash and a large number of blisters. You can also inject the corticosteroid directly into a person’s muscle to prevent the reaction from progressing further.

The person shouldn’t scratch the rash or pop blisters as this can lead to infection. If the rash becomes infected, a doctor may prescribe oral or topical antibiotics.

Various preparations that people can use before and after exposure to poison ivy can be purchased online:

Some people use natural antihistamines for their allergies. Find out more here.

Share on PinterestGardeners should wear gloves when working near poison ivy areas.

Those at highest risk of a poison fire reaction include those who spend a lot of time outdoors, either for work or hobbies, as it can increase exposure.

Some of the people to whose work she may be exposed to poison ivy include:

  • Foresters and farmers
  • Gardener and landscaper
  • construction worker

Tips to reduce risk

A person can reduce their risk of a poison fire reaction by:

  • Learn to identify the plant so that it can avoid it
  • Wear long pants, socks, and gloves when working or engaging in activities outdoors
  • Clean all clothing and shoes after being outdoors if poison ivy is around
  • Immediately after possible exposure, wash the skin with water and rinse thoroughly
  • Scrubbing under the nails after possible exposure
  • Thoroughly clean pets if they have come in contact with poison ivy as they can carry urushiol on their skin and fur

Pets can also be sensitive to the toxin, so people should keep them away from poison ivy whenever possible.

Even a person who is typically unresponsive should wear gloves and be careful when handling poison ivy, as the risk of a reaction increases with age and repeated exposure.

You should also be careful to take off your outdoor clothing and wash it thoroughly, as the juice on your clothing can be transferred to other people who may have a reaction.

Products are available as both a pre-exposure barrier and post-exposure relief. Applying a skin cream containing bentoquatam (IvyBlock) before exposure can help keep urushiol from affecting the skin

Some homeopathic products, like Be away Poison Ivy, claim to relieve symptoms of a poison ivy reaction. However, the National Institutes of Health note that the Food and Drug Administration (FDA) did not evaluate this drug on the basis that there was no scientific evidence of its use.

Poison ivy is a common plant in North America and causes an allergic reaction in many people. If the reaction is severe, it can be life threatening.

People should learn how to spot poison ivy, find out where it grows in their environment, and make sure they know what to do if exposure occurs.

Q:

I have reacted strongly to poison ivy in the past. Do you recommend using over-the-counter products to prevent a reaction?

A:

The best way to prevent a reaction to poison ivy is to avoid the urushiol allergen and to protect your skin.

The American Academy of Dermatology also recommends using a topical treatment with bentoquatam, which can help prevent the skin from absorbing urushiol. There are other homeopathic medications some have found helpful in preventing a reaction.

These drugs require more study to confirm their safety and effectiveness before a doctor can recommend them. As always, it is important to speak to a doctor or dermatologist before taking any new medications, including over-the-counter drugs.

Owen Kramer, MD Answers represents the opinions of our medical experts. All content is for informational purposes only and should not be viewed as medical advice.

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