Poison ivy, poison oak, and poison sumac are three of the most common causes of allergic skin reactions (contact dermatitis) in North America. When these plants cause a skin reaction, it is called Rhus dermatitis.
These plants, from the genus Toxicodendron (which means "poison tree"), produce oil called urushiol, which triggers the allergic reaction. Patients who are allergic to these plants may experience a rash that consists of swollen, itchy, red bumps, and blisters that appear wherever the oil has touched the skin. The oil may also cause an allergic reaction if it is transferred from pets, clothing, shoes, camping gear, or gardening tools to the skin.
These plants grow in wooded areas (forests) throughout the United States, except for Alaska, Hawaii, and some areas of Nevada. The itchy and sometimes painful rash caused by contact with these plants occurs most frequently during the spring, summer, and early fall, when individuals are most likely to spend time outdoors.
An estimated three out of four people are allergic to the oil found in these poisonous plants, according to experts, although the degree of sensitivity varies among individuals. Some people will experience a quick reaction immediately after coming into contact with very small amounts of urushiol, while others may require large amounts of urushiol for a reaction to develop.
Researchers estimate that 85% of all people will develop an allergic reaction to poison ivy if they are adequately exposed to the oil. Adults who have not been exposed to poison ivy only have a 50% chance of developing an allergy to poison ivy. For unknown reasons, about 15% of people appear to be resistant to developing an allergic reaction.
The saying, "Leaves of three, let it be," is often used to describe the physical appearance of poisonous plants. However, not all three-leaved plants contain urushiol, and some that are poisonous have more than three leaves. For instance, while poison ivy usually has three leaves, they may also appear in groups of fives or sevens.
Individuals should learn what each of these plants looks like in order to prevent coming into contact with them. Topical creams like bentoquatam (IvyBlock©), are available over-the-counter and may help prevent or reduce allergic rashes caused by poison plants. If individuals suspect they have come into contact with any of these plants, they should wash exposed skin with soap and water.
Allergic individuals usually develop the rash within 24 to 48 hours after contact with the oil. However, it can take up to several days for the rash to appear. The rash will heal on its own in about five to 30 days, depending on the severity of the symptoms. If symptoms are mild, a cool shower, cool compress, or cool bath with baking soda or oatmeal may help relieve the itching and dry blisters. Medications, such as hydrocortisone or antihistamines, may help relieve itching and swelling. If the rash covers a large area of the body, or it is near the eyes, a healthcare provider may prescribe oral corticosteroids to reduce inflammation and itching.
Some individuals may develop a severe, life-threatening reaction called anaphylaxis. The most serious symptoms of anaphylaxis include low blood pressure, breathing difficulties, shock, and loss of consciousness. Anaphylaxis is a medical emergency that requires immediate treatment with a medication called epinephrine.
TYPES OF PLANTS
Poison ivy: The Latin name for poison ivy is Toxicodendron radicans. This plant may grow as a vine on trees and other surfaces, up to about 50 feet high. It may also grow as a shrub, reaching a height of about four or five feet.
Poison ivy is a hardy plant that can grow in many different conditions. It thrives in areas like sand, stony, or rocky shores of streams, rivers or lakes. It is also commonly found in thickets along the borders of wooded areas and in forest openings.
Poison ivy leaves are typically arranged in groups of three, but the leaves may also appear in groups of five or seven. The leaves in each cluster are about the same size, ranging from one-half inch to two inches long. The edges of the leaves may be slightly notched or smooth. The leaves are shiny and turn bright red in the fall.
Poison ivy produces flowers, which are yellowish to greenish white and about one-quarter inch wide. These flowers grow in clusters on a thin stem.
Small, berry-like fruits appear after the flowers have faded. These fruits are white or green in color and about one-sixth of an inch wide.
Poison oak: The Latin name for poison oak is Toxicodendron diversilobum. This plant has leaves that are lobed like those of an oak tree. Poison oak leaves are slightly larger than poison ivy's, and they grow in clusters of three, five, or seven. The plant's flowers and fruit are also similar to those of poison ivy. Poison oak may grow up to three feet high as either a shrub or a vine. Poison oak leaves have short, smooth hair on the undersides. This plant also produces berries, which are fuzzy and white. Even though poison oak loses its leaves during the winter, the plant remains poisonous year round because the vines also contain urushiol.
Poison sumac: The Latin name for poison oak is Toxicodendron vernix. This poisonous plant is less widespread than poison ivy and poison oak. The plant is most common in the Midwest. It can grow as tall as a tree or shrub with clusters of seven to 13 leaves. The leaves are arranged in pairs, with one leaf at the end. Poison sumac also produces small, yellowish flowers that grow in clusters. The flowers mature into berries that are white to green in color. Clusters of berries may grow up to 12-inches long.
There is also a species of sumac that is not poisonous. The nonpoisonous sumac plant has red berries.
All three plants cause an allergic skin reaction (contact dermatitis) by the same mechanism of action. Poison ivy, oak, and sumac all contain an oil called urushiol. This oil is not actually a poison, but it is made of chemicals that are allergens (substances that can cause an allergic reaction).
Typically, an allergic response is not triggered the first time the body encounters the allergen. In fact, some people can be repeatedly exposed to the allergen before an allergy develops. The first time or several times after the body is exposed to an allergen, the immune system becomes sensitized. During this process, the body's white blood cells develop immunoglobulin E (IgE) antibodies to the allergens in the plant oil. Once sensitized, the antibodies quickly detect and bind to the urushiol allergens in the body. These antibodies also trigger the release of chemicals (like histamine) that cause allergic symptoms like runny nose, watery eyes and sneezing, as well as anaphylaxis. Anaphylaxis is a systemic allergic reaction, which means that many parts of the body are affected. Symptoms of anaphylaxis can vary from mild to severe and may be life threatening. The most dangerous symptoms are low blood pressure, breathing difficulties, shock, and loss of consciousness, all of which can be fatal.
Urushiol is present in the stems, leaves and roots of these plants. The oil is released when the outer layer of the plant is broken. Even the smallest scrape or break in this layer can release the oil.
While these plants can cause allergic reactions year round, it is most likely to occur during the spring and summer, when the leaves are tender or bruise easily.
Individuals do not have to touch the plants directly to develop an allergic reaction. The oil is sticky and long lasting. It can be carried on clothing, shoes, or pets. The oil can then be transferred onto the skin and cause an allergic reaction.
Even in very dry conditions, the oil can still cause a reaction for several years. Dead plants can also cause an allergic reaction.
An allergic rash may develop immediately after contact with the oil or several days after contact.
The rash caused from these poisonous plants is not contagious. The rash can only be spread to other parts of the body or to another person if the oil comes into contact with the skin. Neither the blisters on the skin nor the fluids they secrete contain urushiol. Sometimes, if more than one area of skin comes into contact with the skin, one area will develop a reaction quicker than another. This is because certain areas of the skin are thicker than others. Individuals who develop a rash are advised to wash exposed areas of skin with soap and water to prevent the rash from spreading.
Inhaling smoke from burning poisonous leaves can cause an allergic reaction in the airways and lungs. This can cause difficulty breathing, and blisters inside the lungs that may be very painful. Individuals should seek medical care immediately.
The rash from poison ivy, oak, and sumac usually develops within 24 to 48 hours after contact with the oil. However, it can take up to several days for the rash to appear.
A red, itchy and bumpy rash develops on areas of the skin where oil touched. The rash develops the quickest on parts of the body where the skin is the thinnest (like the wrists, ankles, neck, and face).
The worse phase of the rash typically occurs within one week of exposure. During this time, itching may be severe. The bumps on the skin turn into blisters, which may secrete a clear, yellowish fluid. Within a couple weeks, the blisters begin to crust over and dry up as the rash subsides.
Depending on how severe the rash it, it may take anywhere from five to 30 days for the rash to completely resolve.
Some individuals may experience a severe allergic reactions to poison ivy, oak, or sumac. If the rash covers more than one-quarter of the body, the allergens in the plant oil may cause a systemic reaction called anaphylaxis. Symptoms of anaphylaxis can vary from mild to severe and are potentially deadly. The most dangerous symptoms are low blood pressure, breathing difficulties, shock, and loss of consciousness, all of which can be fatal. Patients should seek medical attention immediately if they experience a severe rash, as well as fever, headache, or nausea, trouble breathing or shortness of breath, extremely painful rash that interferes with normal activity, or enlarged lymph nodes.
An allergic reaction to a poison plant is diagnosed when patients experience the typical allergic symptoms and develop the characteristic rash on the skin. Affected areas of the skin will be red and itchy. Oftentimes, the rash appears in patches or streaks where the plant brushed against the skin. Red bumps and oozing blisters may also be present.
PROCEDURE AFTER EXPOSURE
Clothing should be removed and washed with detergent in warm water. Dry cleaning clothes will also eliminate the oil from clothing.
Wash all exposed areas of skin with soap and cool water. Using soap and water within 30 minutes of possible contact may prevent an allergic reaction. In the woods, water from a stream may effectively wash away the oil. Using water alone within five minutes of possible contact with the plant may prevent an allergic reaction.
Bathe pets exposed to the plants.
Wash any camping gear, garden tools, or other items that may have come into contact with urushiol.
General: At the very first sign of a rash, individuals should wash the affected skin with soap and cool water. Most rashes caused by poison ivy, poison oak, or poison sumac are mild and last from five to 12 days. In severe cases, the rash can last for 30 days or longer. Treatment should begin as soon as symptoms develop. Individuals who begin to experience symptoms of anaphylaxis, a severe allergic reaction, should seek medical attention immediately.
gel: Aloe vera gel has been applied to affected areas of the skin to relieve itching and help rashes heal. Aloe vera gel should not be applied to open cuts, blisters, or sores on the skin.
Antihistamine: Oral antihistamines like diphenhydramine (Benadryl©) can help reduce itching.
Banana peel: Traditionally, the inside of a banana peel has been rubbed on affected areas of the skin to relieve itching. However, the efficacy of this treatment has not been scientifically studied.
Baking soda: A solution of baking soda and water may help treat allergic skin reactions caused by poison plants. Three teaspoons of baking soda has been mixed with one teaspoon of water and applied to affected areas of the skin.
Calamine lotion: Calamine lotion (Calamox©) can be applied to the skin to reduce itching and blistering.
Cool showers: Taking cool showers can help relieve itching associated with the allergy. Also, soaking affected areas in cool water with baking soda or oatmeal may help reduce itching and dry blisters. Colloidal oatmeal (Aveeno© Oatmeal Bath) has shown to relieve itching up to seven hours.
Cool compress: Applying a cool compress to affected areas of the skin may help relieve itching.
Epinephrine: Epinephrine is used to treat anaphylaxis. Epinephrine is injected and acts as a bronchodilator because it dilates the breathing tubes. It also constricts the blood vessels, which increases blood pressure. Patients who experience anaphylaxis may also be admitted to the hospital to have their blood pressure monitored and possibly to receive breathing support. Other emergency interventions may also include endotracheal intubation (placing a tube through the nose or mouth into the airway) or emergency surgery to place a tube directly into the trachea (tracheostomy or cricothyrotomy).
Individuals with a history of severe food allergies should carry a prescription epinephrine auto-injector. If symptoms of anaphylaxis appear after exposure to an allergen, the patient uses the device to inject the epinephrine into his/her thigh. A trained family member of friend may help the patient administer the epinephrine, if necessary.
Hydrocortisone: Hydrocortisone cream may be applied to the affected area to temporarily relieve itching. Hydrocortisone 1% cream, which is available over-the-counter, has anti-inflammatory effects and relieves swelling and redness in addition to itching. Prescription hydrocortisone has been used to relieve itching, redness, dryness, crusting, scaling, inflammation, and discomfort associated with the reaction.
Oral corticosteroid: Patients should consult their healthcare providers if a severe rash develops. An oral corticosteroid may be prescribed as a short-term treatment to reduce swelling and lessen itching. Patients should slowly taper off medication to avoid serious side effects.
Vinegar: White distilled vinegar or apple cider vinegar has been applied to affected areas of the skin to relieve itching.
Traditional or theoretical uses lacking sufficient evidence
: Chamomile has been reported to have wound healing and anti-inflammatory properties and has been used to treat poison ivy. However, there is a lack of human evidence on the safety and effectiveness of this treatment.
Avoid if allergic to chamomile. Anaphylaxis, throat swelling, skin allergic reactions, and shortness of breath have been reported. Chamomile eyewash may cause allergic conjunctivitis (pinkeye). Stop use two weeks before and immediately after surgery/dental/diagnostic procedures with bleeding risks. Use cautiously if driving or operating machinery. Avoid if pregnant or breastfeeding.
Pantothenic acid (vitamin B5)
: Pantothenic acid (vitamin B5) has been suggested as a treatment for allergic reactions to poison ivy. However, there is a lack of human evidence on the safety and effectiveness of this treatment.
Avoid if allergic or hypersensitive to pantothenic acid or dexpanthenol. Avoid with gastrointestinal blockage. Pantothenic acid is generally considered safe in pregnant and breastfeeding women when taken at recommended doses.
: The leaves of Plantago ovata (psyllium) have been used in many folk medicine traditions to treat inflammatory skin conditions and have been used to treat poison ivy. However, there is a lack of human evidence on the safety and effectiveness of this treatment.
Avoid if allergic or hypersensitive to psyllium, ispaghula, or English plantain (Plantago lanceolata). Avoid in patients with esophageal disorders, gastrointestinal atony, fecal impaction, gastrointestinal tract narrowing, swallowing difficulties, and previous bowel surgery. Avoid ingestion of psyllium-containing products in individuals with repeated or prolonged psyllium exposure who have not manifested allergic or hypersensitive symptoms. Prescription drugs should be taken one hour before or two hours after psyllium. Adequate fluid intake is required when taking psyllium-containing products. Use cautiously with blood thinners, antidiabetic agents, carbamazepine, lithium, potassium-sparing diuretics, salicylates, tetracyclines, nitrofurantoin, calcium, iron, vitamin B12, other laxatives, tricyclic antidepressants (amitriptyline, doxepin, and imipramine), antigout agents, anti-inflammatory agents, hydrophilic agents, and chitosan. Use cautiously with diabetes and kidney dysfunction. Use cautiously if pregnant or breastfeeding.
: Traditionally, slippery elm has been used to treat allergic reactions to poison ivy. However, there is a lack of human evidence on the safety and effectiveness of this treatment.
Avoid if allergic or hypersensitive to slippery elm. Avoid if pregnant or breastfeeding.
: Traditionally, wheatgrass has been used to treat allergic reactions to poison ivy. However, there is a lack of human evidence on the safety and effectiveness of this treatment.
Avoid if allergic or hypersensitive to wheatgrass. Use cautiously because wheatgrass is grown in soils or water and consumed raw, and it may be contaminated with bacteria, molds, or other substances. Use cautiously if pregnant or breastfeeding.
: Witch hazel (Hamamelis virginiana) is a flowering shrub, native to Eastern North America although other related species exist in North America, Asia, and Europe. Although witch hazel has been suggested as possible treatment for allergic reactions to poison ivy, human evidence is lacking.
Avoid if allergic or sensitive to witch hazel. Avoid if pregnant or breastfeeding. Use cautiously in people with liver or kidney disorders, diabetes, and in children.
Individuals should learn what poison ivy, oak, and sumac look like in order to prevent contact with the plants.
Individuals who are allergic to poisonous plants should wear long pants and long-sleeved shirts when they are in wooded areas.
Topical creams like bentoquatam (IvyBlock©) are available over-the-counter and may help prevent or reduce allergic rashes caused by poison plants. The cream is applied to exposed areas of skin before possible exposure to poison ivy, poison oak, or poison sumac. The cream should not be applied to open cuts, sores, or wounds.
If a poisonous plant is growing near the home, individuals should remove it carefully. Wear long pants, long sleeves, heavy work gloves, and closed shoes or boots. The plant should be removed from the roots. Put the plant in a tightly sealed plastic bag and dispose of it. Never burn the plants because inhaling the smoke can cause an allergic reaction to occur in the airways or lungs. Wash all clothing, including all gardening tools that may have come into contact with poison plants, with warm water once the plant is removed.
Individuals with a history of severe allergic reactions should carry a prescription epinephrine auto-injector. If symptoms of anaphylaxis appear after exposure to a poison plant, the patient uses the device to inject the epinephrine into his/her thigh. A trained family member of friend may help the patient administer the epinephrine, if necessary.
Do not let pets run freely through wooded areas where poison plants may grow.
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
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