Now that the summer months are almost here, the unlucky amongst us should learn to recognize and avoid those infamous plants that cause us to suffer from skin rashes, swelling, itching, and sometimes severe allergy or anaphylaxis upon contact with the plant. The mechanisms of rash development is actually from a complex immunological reaction that our bodies develop against the allergen, a true allergy called Allergic Contact Dermatitis.
Everyone has heard of Poison Ivy, Oak, and Sumac, but not everyone knows what these plants look like or methods of preventing contact with the allergen. 70 to 85% of the population has been sensitized and thus can potentially get the rash, with it actually affecting about up to 50 million Americans. In Texas, it is mainly Poison Ivy that causes Allergic Contact Dermatitis.
• Poison Ivy is a weed with three shiny green leaves and a reddish stem, with either small green flowers or green-white berries. The leaves can have either smooth or serrated edges. It grows as bushes, plants, or vines. It is found throughout the US except in the Southwest, Alaska, and Hawaii.
• Poison Oak also has the same three-leafed structure, but grows as a shrub on the West Coast but can be found in the Eastern US as well (rarer in Texas).
• Poison Sumac is a woody shrub with each stem having 7-13 leaves arranged in pairs. It mainly grows in standing water in the peat bogs/swamps of the Northeast, Midwest, and Southeast.
The common denominator of these plants, all part of the Toxicodendron Genus of plants, is an allergen called urushiol, an oily resin. Sensitized people will get the rash within 12-48 hours after contact, and the rash can persist for 3 weeks. The rash is uncommon in children less than 7 years old, and rare in infants, due to undeveloped immune systems.
While the rash is not “contagious” in the strictest sense from one person to the next, the oily resin adheres to everything that comes in contact with the plant. Thus, these items , including freshly contaminated skin, pets (animals do not get the rash), clothing, and tools, must be washed or that allergen can continue to cause rashes. If left on inanimate objects, the resin can be allergenic for years. Even smoke from these burning plants can transmit the resin and irritate eyes, oral, and nasal passages.
Scratching the blisters does not spread the rash; the appearance that the rash is “spreading” is due to your skin responding at different rates from the initial contact with the plant. Washing affected skin with isopropyl alcohol and/or soap and water can only prevent the allergy if it is done within 10 minutes after contact with the resin. For those who are extremely sensitive, there is a product called “Ivy-Block” that can be placed on the skin prior to anticipated contact with the plant. This topical product contains 5% bentoquatam, a compound that prevents penetration of the resin into the skin.
Most people get mild skin reactions treatable with over-the-counter medications such as oral antihistamines like Benadryl®, calamine lotion, hydrocortisone cream, and cool soaks. People should see their physicians if the rash is severe or widespread, if it affects eyes, nose, mouth, or genitalia, if the rash gets infected, if you get a fever of 100°F or greater, or if the rash does not improve after 3 weeks. These patients may need very strong topical preparations, oral prednisone, and/or antibiotics.
Roopal Bhatt,MD is a practicing Dermatologist in the Four Points Area. To reach her about questions on this subject or another,
please contact her at contact@fourpointsdermatology.com
