by Dr. Kathryne Buege
Well, the odds were not in you favor and you have been thrown back into the ring. This time, the plants of the Anacardiaceae family have your name and number. They are prepared for this match and guarantee an exciting conclusion to the “Itching Games.”
With what are we dealing? In the United States, the most important members of this family are those of the genus Toxicodendron (“poisonous tree”). Common or northern poison ivy, western poison ivy, eastern poison oak, western poison oak, and poison sumac comprise this genus.
How do we identify the plant?
“Leaves of three, let them be” is a helpful reminder in helping identify these types of plants. Poison ivy and poison oak are often identified by three leaflets with flowering branches arising from axillary positions on a single stem. The leaves may be green or green-reddish and are smooth, fine-toothed, or lobed margins. They have small, yellow green flowers and cream colored fruit, which look like berries and are most often seen in the fall.
In contrast, poison sumac more often forms leaflets of five, seven or more that angle upward toward the top of the stem.
One may also find characteristic black dots on all of these plants; this black lacquer is oxidized urushiol found on the plant leaves within 10 minutes of exposure to oxygen. Many people are sensitive to urushiol, the allergic component. It is a sticky oil, and causes the rash by contact.
- You can get the rash from touching or brushing against any part of these plants and then contacting the skin. This can include clothing, sporting gear, gardening tools or even pet fur –
YES, pet fur. My mother had poison ivy dermatitis on her abdomen, and it was not from wearing a bikini in the woods (sorry mom)…her fluffy white dog Mimi was the culprit!
- The rash is only spread through the oil. You CANNOT catch a rash from someone else by touching them or their blister fluid.
- The rash is an allergic reaction to the oil. You become allergic to it through contact and your immune system may start to react to the oil as though it’s a harmful substance.
- Symptoms of poison ivy dermatitis in sensitized individuals generally develop within 4-96 hours after exposure and peak between 1 and 14 days after exposure.
How do I get a rash in places I did not contact the plant/urushiol?
- Lesions may present at different locations at different times after exposure based upon the amount of urushiol present and thickness of the skin involved. This can give the impression that the poison ivy is spreading from one region to another. Blister fluid is not antigenic (contagious). Also, new lesions can present up to 21 days after exposure in previously unexposed individuals.
- Rebound dermatitis (recurrence of rash) may occur if too short a course of steroid is used, for instance, a six-day course in a Medrol dose pack. Basically, your body has cells that react and activate an immune response, leading to a rebound rash when steroids are stopped.
Intense itching and redness are the most common presenting signs of poison ivy dermatitis. Patients may develop blisters or papules, arranged in linear or streak-like configurations where the oil has contacted the skin.
- Involvement of the face and genitals may cause significant edema (swelling) and discomfort.
- Runners, campers, and outdoor-enthusiasts: beware of what you come in contact with if nature calls unexpectedly.
- The rash may take more than a week to show up the first time you have a reaction to the oil. If develops sooner with later contacts after your initial exposure. You will only get a rash where the oil touched your skin, but as I mentioned earlier, there are a few exceptions.
What to do? Treatment and Prevention
The most important and effective treatment for poison ivy dermatitis is identification and avoidance of toxic plants and related allergens.
- Protective clothing is useful, but patients should be reminded that clothing, pets and fingernails can harbor the allergic resin for many days. The oil can seep through clothing and can penetrate rubber or latex gloves, but not heavy-duty vinyl gloves.
- Burning poison ivy is not recommended. The oil is stable at high temperatures and the plant particles dispersed in smoke are allergenic and irritant.
- After a known exposure, patients should remove any contaminated clothing and gently wash skin with mild soap and water ASAP. Vigorous scrubbing is not useful and can exacerbate the impending dermatitis.
- Chemical in-activators to prevent poison ivy (Tecnu) and oil removing compounds (Goop) are helpful, but expensive. Most healthcare providers suggest washing with an inexpensive mild detergent.
- Barrier creams are controversial. Most studies suggest Ivy Block, an organoclay compound, is useful for preventing poison ivy. It must be reapplied every four hours and leaves a clay residue on skin.
- DO NOT USE: Antihistamines applied to skin (topical – cream, spray or gel), topical anesthetics (benzocaine/Lanacane), or topical antibiotics that contain Neosporin/neomycin.
- These may cause an allergy problem of their own in certain patients.
- Mild rashes may be treated with calamine lotion, oatmeal baths, and cool, wet compresses.
- Weeping lesions may be treated with topical astringents such as Burow’s solution or Domeboro used under occlusion to help dry the lesions.
- A soap misture of Zanfel may benefit.
- Corticosteroid pills, injections or creams may be prescribed for more severe reactions/rashes.
- An oral dose of prednisone should be tapered over 14-21 days, but is reserved for more extensive cases of poison ivy dermatitis.
- Sedating antihistamines (Benadryl and sometimes Zyrtec) are used to help people with severe itching to sleep. However, the itching in poison ivy is not caused by histamine release and there is little to no evidence to support their use.
The most important advice is to prevent exposure. Learn to identify these plants. Use protective clothing and use heavy-duty vinyl gloves. Wash with a mild detergent soap ASAP after exposure. For more severe or persistent rashes, seek medical attention with your primary care provider or MASH Urgent Care. Having said this, hopefully your name won’t get picked for the “Itching Games,” but if it is – you will be prepared for battle. Enjoy the rest of your summer, Buffalo.