Poison Ivy (and its relatives) are the single most common cause of allergic reactions in the United States. Each year 10 to 50 million Americans develop an allergic rash after contact with this poisonous plant.
What is Allergic Phytodermatitis?
Phyto- (plant) -dermatitis (inflammation of the skin) is frequently seen in hikers and campers, home gardeners, and children active in the outdoors. It is also a common occupational disorder. It results from an allergic reaction to contact with plants containing the chemical compound urushiol (pronounced oo-roo-she-ol).
- Urushiol is an oily, resinous compound found in all parts of the poison ivy plant (except the hairs, anthers and pollen).
- The amount of urushiol it takes to cause a reaction is measured in nanograms (one billionth of a gram). Most sensitive people react to as little as 100 nanograms, so it doesn’t take much.
- Allergic reaction to urushiol occurs in over half the people in the US. Most others will be sensitized after just one exposure. Even for those who claim they never get poison ivy, repeated exposure is tempting fate.
Reaction and treatment
A typical progression in the reaction to exposure is:
- Within two days of contact, infected areas become itchy and turn red, and swelling may occur. The tell-tale streaky pattern of the infected skin results from scratching with fingers that still have urushiol resins trapped beneath the nails.
- Blisters may form within two more days, which, in turn, may be followed by bursting and oozing. Contrary to the commonly held belief, ooze from the blisters is not infectious. Spreading occurs because of touching the original oils still carried on clothing, gardening gloves, tools and pets.
- Healing can take two to four weeks depending on exposure and the individual.
In the case of poison ivy, an ounce of avoidance is worth the proverbial pound of cure.
- Learn to recognize poison ivy’s characteristic, “leaves of three,” and avoid contact.
- Protective clothing and commercially available barrier creams can also be effective.
- If contact is unavoidable, solvents such as rubbing alcohol can be effective in breaking down the oils that carry urushiol. Use the solvent prior to washing and rinse with strong soap and cold water.
- In severe cases, Dr. Miller may prescribe the use of steroid creams.