"Leaves of three, let them be!"

Summer is a common time for skin allergies to flare. The potential for rashes from poison oak, poison sumac or poison ivy, in particular, increases as we spend more time outdoors, but atopic dermatitis (eczema) and urticaria (hives) are also common.

This summer, with its incredibly high temperatures, humidity and increased carbon dioxide concentrations, the growth of poison ivy and related plants appears to be exceedingly potent, says Leonard Bielory, M.D., an allergy specialist with the Rutgers Center of Environmental Prediction at the School of Environmental and Biological Sciences, in New Brunswick, NJ. Bielory is also an allergy and immunology attending physician at Robert Wood Johnson University Hospital in New Brunswick.

Poison oak, poison sumac or poison ivy can all lead to skin rashes. For folks picnicking or hiking though parks and open spaces this summer should beware certain plants, cautions Bielory. “I use a simple reminder for residents to stay safe in the outdoors: ‘Leaves of three, let them be!’”

This is true for poison ivy and poison oak, each of which has three leafs in a single cluster. On the other hand, poison sumac has seven to 13 leaves on a branch. “Some people are sensitive to the point where their conditions can flare up in simple contact with grass or other plants,” says Bielory. “As a general rule, wear long pants and long sleeves for protection to lessen your chances of getting a reaction to outdoor plants, especially poison ivy, poison oak or poison sumac.”

Bielory offers the following steps that may help to reduce symptoms of atopic dermatitis and hives, or even avoid them all together:

• Beware of the sun. Hives can be triggered by heat or sweat. Drink plenty of fluids, avoid becoming too hot and wear sunscreen.
• Be prepared. Eczema can worsen in the summer, especially with excess sweating. Have a skin care treatment plan. This may include having mild bathing products on hand.
  

Unlike pollen or bee sting exposure that can cause immediate reaction—sometimes within minutes or seconds of exposure—poison ivy allergy occurs through the T-cell immune system and can manifest days after exposure.

According to Bielory, there are several myths associated with poison ivy dermatitis.

Myth 1: Poison ivy rash is contagious.
False: Poison Ivy is not contagious and the rash only spreads if you spread the oil (urushiol) from the plant. Urushiol is the sticky, resin like substance that oozes from the plant including its leaves.

Myth 2: Poison ivy cannot be transmitted from dead plants.
False: Only 1 nanogram (billionth of a gram) of urushiol oil is needed to cause a rash. It can stay active on any surface, including dead plants, for as long as five years. For example, a person can get poison ivy from their pet dog that has been running in the backyard or woods and has oil on its coat. That oil can be transmitted through petting the dog.

Myth 3: Breaking the blisters of poison ivy dermatitis releases urushiol oil that can spread the rash.
False: However, open blisters or vesicles may become infected, leading to scarring of the skin.

Myth 4: A person can become immune (desensitized) when exposed multiple times to poison ivy.
False: Some people seem not to react to poison ivy–at least not on first exposure. It may take longer than 2-3 days for the immune response to generate the dermatitis that occurs, sometimes as much as to 7-10 days. Over 90% of the U.S. population is sensitive to the urushiol oil. The greater the exposure to urushiol oil, the more likely it is for a person to develop a reaction to poison ivy.