Thinking Big about Poison Ivy

Q&A with Fred Procopio, Medical Director of URI’s Health Services

How prominent a problem is poison ivy in our area?

Poison Ivy, Sumac and Oak are the most common cause of allergic reaction in the United States. These are plants in the Toxicodendron genus. Poison Ivy is most common in the eastern United States while Poison Oak is more common in the west. Poison Sumac is more likely seen in less inhabited areas with flooded soils such as marshes and swamps.

Problems with Poison Ivy are most prominent during the spring and summer. However you can get Poison Ivy any time of the year associated with clearing brush and cutting vines, carrying and burning wood, gathering vines for ornamentation such as wreaths, and examining the greenish white berries that appear in autumn. I have had patients with Poison Ivy in the middle of winter.

What causes the itchy rash?

The symptoms are caused by a chemical, urushiol, present in the sap. This is easily contacted from damaged or broken plants, even from dead or decaying plant material or from surfaces that have contacted the chemical, such as clothing, tools and pets. It is also easily contacted from the smoke of burning Poison Ivy plants. This allergy producing chemical can remain active on plant material and surfaces for years.

The rash can occur from a few hours after exposure up to many days later depending on previous exposures and reactions. Symptoms can continue to develop/persist for up to 21 days.

What should students do to avoid coming into contact with it?

First and foremost, one must learn to recognize, identify and avoid Poison Ivy. Many are familiar with the phrase, “Leaves of three, let them be.” This is helpful, but, unfortunately, Poison Ivy can be found in many forms including woody shrubs as well as vines or low growing plants. The leaf is made up of three leaflets with the center leaflet generally larger than the other two. Poison Ivy can produce yellowish green flowers in early to mid summer, and small greenish, white berries in autumn.

Protective clothing can be helpful, but the oil can remain present on clothing, pets and under fingernails. It can penetrate clothing and rubber/latex gloves, but not vinyl.

Barrier creams containing bentoquatam (Ivy Block®) may be helpful, but must be applied at least 15 minutes before exposure and must be reapplied every four hours if exposure continues. This leaves a clay like residue on the skin that decreases penetration of the urushiol.

Avoid exposure to smoke that might contain Poison Ivy plant material.

If you contact poison ivy, what should you do?

It is important to wash the area with soap and water as soon as possible after exposure. Much of the urushiol can be absorbed within 10 minutes. However, washing up to two hours later has been shown to be beneficial. Never-the less, the sooner the better is recommended. Fingernails should be carefully cleaned to remove remaining resin that can be spread by touching and scratching.

Vigorous scrubbing is to be avoided as this could worsen the impeding dermatitis (rash).

Studies have shown that use of a chemical inactivating compound such as Tecnu® and a topical surfactant such as Dial® ultra dishwashing soap are effective when used up to two hours after exposure. However, it was not clear that these expensive measures are clearly more effective than soap and water.

Clothing and tools should be washed with warm soapy water.

If you get poison ivy, what should you do?

There are not many studies that prove effective treatment for Poison Ivy. However, clinical experience supports the following measures.

Soothing treatments such as oatmeal baths, cool wet compresses, and application of calamine lotion provide some symptomatic relief. Topical astringents such as Burrow’s solution or Domeboro® may help dry weeping rashes.

I recommend avoiding topical antihistamines such as diphenhydramine, topical anesthetics such as benzocaine, and topical antibiotics such as neomycin because they have their own allergenic potential. Some clinicians suggest the topical use of pramoxine is better tolerated and helpful with controlling the itchy symptoms.

Oral antihistamines are not effective for Poison Ivy because the rash is not caused by histamines. Therefore, non-sedating antihistamines such as loratadine (Claritin®) and cetirizine (Zyrtec®) are not likely to be helpful. Some clinicians feel that sedating oral antihistamines such diphenhydramine (Benadryl®) are helpful for those who have difficulty sleeping due to the itchy symptoms.

Over-the-counter, non-prescription corticosteroid creams such as hydrocortisone are not proven to be effective. High potency, prescription topical corticosteroids can be somewhat helpful if started early before the establishment of vesicles (blisters) but they do not alter the course of the dermatitis. Super-potent topical corticosteroids can alter the course of the dermatitis but can pose risks that should be discussed with your clinician.

If you have severe symptoms, particularly if this involves the face or genital region, oral or injected corticosteroids should be considered. Such treatment must be prescribed by a medical provider.

Can poison ivy pose more serious problems than blisters and a rash, and feeling itchy?

The vesicles (blisters) of Poison Ivy dermatitis can become infected and require treatment with antibiotics. Inhaled smoke from burning plants can cause lung irritation and severe respiratory symptoms. Rarely, the immune reaction to urushiol can cause kidney damage.

Do you have to be allergic to poison ivy to get it?

Yes, but 85-90% of people will become allergic to poison ivy at some time. Even if you have not reacted to contact with the plant in the past, you might with subsequent encounters. Adults who have never had Poison Ivy have an approximately 50% chance of developing allergy to it if exposed.

Can poison ivy spread from one person to another?

The only way for Poison Ivy to spread from one person to another is for one person to spread the urushiol chemical to another by direct contact. This can occur by touching a person with hands that have been contaminated by the plant oil. This can happen with contact with a pet as well. Once the urushiol is washed off, it cannot be transmitted. The fluid from the blisters does not transmit Poison Ivy.

In fact, one does not spread Poison Ivy from one part of the body to another by touching the blisters unless the resin from the plant has remained. That is why it is important to wash off the resin as soon as possible after exposure. This can limit the areas involved and the severity of the involvement. The Poison Ivy is “spread,” originally to locations contacted by the urushiol upon exposure. It only takes tiny amounts to do this. It appears to “spread,” over time depending on the amount of chemical deposited on the skin and the thickness of the skin in the area affected. This process can continue for 2-3 weeks.

Some key points to remember:

Learn to identify and avoid poison ivy.

Wear protective clothing if you may be at risk, such as when clearing plant materials or enjoying recreation in high risk areas.

Avoid inhalation of burning plant materials.

Wash with soap and water as soon as possible after exposure: Within 10 minutes is best, but up to one hour is very helpful. Even washing up to two hours later has benefit.

Consider use of a barrier cream such as Ivy Block® to prevent Poison Ivy if you have had severe reactions in the past.

Contact a medical provider if you have a history of severe Poison Ivy and you begin to develop symptoms.

Contact a medical provider if you have severe symptoms or if the rash involves the face or genitals.