Poison oak contains a substance called urushiol that causes contact dermatitis. Urushiol is a gooey oleoresin produced in the stems, roots, leaves and flowers of the poison oak plant. Contact dermatitis refers to a skin inflammation caused by contact with an allergen or irritant, such as urushiol. The symptoms can become intensely aggravating.
Rash
Redness is one of the first signs of contact with poison oak. The initial redness can appear as a single straight line where the edge of a leaf brushed the skin. It can also appear in blotchy patterns if skin comes in contact with contaminated clothing, tools or other items.
Tiny blisters may form several days after the rash first appears. These blisters may weep small amounts of liquid. Scabbing may occur, particularly if the area is scratched. The inflamed area can become swollen and hot.
New areas of rash may break out several days or more after initial exposure. Although this seems like the rash has spread, the Merck web site attributes this to differences in "the rate at which your skin absorbed the urushiol. "
Itching
The itching caused by the poison oak plant can become enormously irritating. Itching occurs wherever the rash forms. Severe cases can feel almost as if the skin was repeatedly pricked by tiny needles. The desire to scratch can prove hard to resist.
The duration of the itching varies from weeks to over a month. In many cases, application of calamine lotion, cortisone cream or ointments containing diphenhydramine can provide temporary relief. Serious cases that involve large portions of the body are treated with oral prednisone.
Leathery skin
The affected area can become dry and leathery, particularly if the area has been scratched. Skin can become temporarily discolored and turn slightly darker. Long-term scarring proves rare.
The leathery texture of the skin often outlasts the itching and rash in some patients. It is best treated by regular application of hand lotion or other moisturizers.
Warnings
Serious cases are unlikely to resolve by themselves without professional attention. Fortunately, treatment proves quick and effective. Contact a doctor if symptoms don't go away within a week or so, or if a large part of the body is affected.
