Poison ivy is coated with a resin-like sap, which contains a chemical called urushiol. Every part of the plant contains the resin: leaves, stems and roots. Most people only come in contact with the leaves, but it is important to remember the entire plant can produce an allergic reaction, Ray said.
Urushiol produces symptoms in three out of four people. Often the symptoms begin as a severe itching of the skin. Redness, burning, swelling and blistering follow the itching. Severity of the symptoms depends on each individual's sensitivity and reaction to the allergen.
"If you have never been exposed, or are not yet allergic to poison ivy, it may take 10 to 21 days for a reaction to occur the first time," Ray said. "Once allergic to poison ivy, however, most people break out 48 to 72 hours after contact with the plant. Typically, individuals have been exposed at least once, if not several times, before they break out with a rash."
Allergic reactions on the body are often regional. Tough layers of skin--the palms of the hands and the soles of the feet, for example--tend to be more resistant and have less of a reaction than thinner layers of skin, such as the eyelids and underarms, which are very sensitive.
"The severity of the reaction partially depends on the ability of the sap to penetrate the skin," Ray said.
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poison ivy/oak
Urushiol produces symptoms in three out of four people. Often the symptoms begin as a severe itching of the skin. Redness, burning, swelling and blistering follow the itching. Severity of the symptoms depends on each individual's sensitivity and reaction to the allergen.
"If you have never been exposed, or are not yet allergic to poison ivy, it may take 10 to 21 days for a reaction to occur the first time," Ray said. "Once allergic to poison ivy, however, most people break out 48 to 72 hours after contact with the plant. Typically, individuals have been exposed at least once, if not several times, before they break out with a rash."
Allergic reactions on the body are often regional. Tough layers of skin--the palms of the hands and the soles of the feet, for example--tend to be more resistant and have less of a reaction than thinner layers of skin, such as the eyelids and underarms, which are very sensitive.
"The severity of the reaction partially depends on the ability of the sap to penetrate the skin," Ray said.