Poison ivy, which can affect up to 70% of the population, belongs to the Anacardaceae plant family, which contains a chemical allergen known as pentadecyl catechols in the milky sap from the plant. Other plants related to poison ivy (Toxicodendron radians) are poison oak, poison sumac, poison dogwood, Brazilian pepper, cashew nut tree, ginko tree, Indian marker nut tree, mango tree, lacquer tree, rengas tree.
Features of Poison Ivy Dermatitis
- Poison ivy occurs throughout the United States (except extreme southwest) and southern Canada and poison oak on the west coast. Poison sumac and poison dogwood are seen in swampy, marshy areas.
- Outdoor workers in the telephone and electrical departments, farmers and hitchhikers are the persons commonly affected by poison ivy dermatitis. The leaves, stem, seeds, flowers, berries and roots of poison ivy contain a milky sap which turns into a black resin on exposure to air. These oleoresins are known as urushiol which contains the allergen pentadecylcatechols.
- Unroasted cashew nuts contain urushiol and can cause systemic allergic contact dermatitis if ingested by sensitized individuals. Laundry markers cause allergic contact dermatitis, sometimes called the dhobi itch (which also includes ring worm infestation).
- Poison ivy allergic contact dermatitis occurs usually in the spring, summer and fall; can occur year round.
- After first exposure, sensitization occurs in 7 to 12 days. In subsequent exposure, itchy skin rashes can appear within 12 hours.
- Dark skinned individuals are less prone to poison ivy dermatitis than the fair skinned.
- Itching can be mild, or severe. A burning sensation will be felt before the itchy skin rashes appear. Secondary infection can complicate the allergic reaction.
- The skin rashes are usually seen on exposed areas in a linear fashion. A red linear mark, rapidly evolving to bumps and blisters, sometimes with marked swelling resembling cellulitis is the typical presentation of poison ivy dermatitis. The rashes when they dry up, leave crusting and scaling. Healed lesions can leave post-inflammatory pigmentation in the dark skinned.
- The allergen, oleoresin, can penetrate damp clothing to covered areas as well.
- Eating unpeeled mango or unroasted cashew nut can produce allergic contact dermatitis on the lips, face and even the anus and surrounding areas.
Other Diseases Mimicking Poison Ivy Dermatitis
Allergic contact dermatitis to other allergens, especially nickel, chromates and other plants can present with similar features. Sensitization to sunlight (phytophotodermatitis) to many plant products can cause contact dermatitis on exposed areas. Skin soft tissue infections like cellulitis and erysipelas, atopic dermatitis acute exacerbations, inflamed ring worm infestations, early shingles (herpes zoster) and fixed drug eruption can all mimic poison ivy dermatitis.
Treatment of Poison Ivy Dermatitis
Management of allergic phytodermatitis, including that of poison ivy, is similar to that of allergic contact dermatitis due to various causes.
- Thorough washing with soap and water after accidental exposure to poison ivy will reduce the severity of the reaction.
- Acute skin rashes: Wet soaks with potassium permanganate or Burow’s solution.
- Topical steroids (Class I to III), can be used; after controlling the secondary infection with oral antibiotics
- Larger blisters can be drained, but the roof should be preserved.
- Injection of a short acting steroid can abort the poison ivy dermatitis if takes immediately after exposure.
- Antihistamines will help relieve the itching.
- A 1-2 weeks’ course of systemic steroids may be required in severe, generalized poison ivy dermatitis.
It is always beneficial to remember that if one washes the area with soap and water immediately after exposure the poison ivy dermatitis is preventable to an extent.
Reference
Disclaimer
The information given in this article is for educational purpose only so that patients are aware of the options available. No diagnosis should be made or treatment undertaken without first consulting your doctor. If you do so, the author or suite101 will not be responsible for any consequences. The images provided are for illustration purpose only.
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