The most common cause of allergic skin reactions in the United States, the University of Iowa Hospitals and Clinics report, is contact with a substance found in three plants --- poison ivy, poison oak, and poison sumac, according. These plants contain the oil urushiol, which leads to an allergic skin rash in most people when the oil touches their skin. These plants all have shiny leaves in groups of three. Poison oak is not a true oak tree, but a shrub with oak-shaped leaves related to poison ivy and poison sumac.
Contact
A skin rash from poison oak can develop through three types of contact, explains the American Academy of Dermatology (AAD). Direct contact involves touching the plant, while indirect contact involves touching something else that has been in contact with poison oak. This can be nearly any object, including clothing, gardening or other outdoor tools, sports equipment or a pet's fur. In addition, airborne contact can occur from burning poison oak, which releases urushiol particles into the air that can land on skin. Breathing in these particles can cause serious lung irritation.
Precautions
If you realize you've come in contact with poison oak, remove your clothes and shoes as quickly as you can, but be careful not to touch the areas that might be contaminated with urushiol, advises the University of Iowa. Wash your skin well with lukewarm water and soap within 10 minutes of contact. If soap isn't available, rinse your skin well with water. Thoroughly wash anything that might be contaminated with urushiol, including clothing, tools and pets.
Time Frame
Although urushiol penetrates the skin rapidly, the rash typically does not appear for 12 to 72 hours, the AAD reports. Symptoms include severe itching, red blotches, swelling and blisters. The blisters crust over within a few days, and the rash usually clears up within two weeks. The rash may appear to spread, but it does not actually do so; it can simply take longer to develop on some affected areas.
Treatment
To treat a skin rash from poison oak, apply cool compresses and take cool or lukewarm baths or showers to relieve itching and inflammation, the University of Iowa recommends. Add a half-cup of cornstarch, baking soda or colloidal oatmeal to baths for further relief. Avoid scratching, but trim your fingernails so you don't break your skin if you do scratch. Keep affected areas and your fingernails clean to prevent infection. Calamine lotion is good for soothing irritation, but the University of Iowa advises against using lotions or ointments containing antihistamines, anesthetics or cortisone unless approved by your doctor.
More Serious Effects
Some people may develop headache, fever, stomach cramps, nausea or diarrhea along with skin rash after contact with poison oak, which may call for medical attention. Contact your doctor if the rash becomes severe, affects the face or genitals, covers more 20 percent of your body or becomes infected. Swelling of the throat or eyes, overall body swelling or difficulty breathing all require immediate medical attention, the AAD advises. You may need prescription medication to reduce itching and swelling.
