By Drs. Sally Robinson and Keith Bly

Some plants, such as poison ivy, poison oak and poison sumac can cause an allergic reaction in the form of a rash or swelling. An allergic reaction to these plants is caused by a substance called urushiol, which is a colorless, odorless oil that is contained in the plant's leaves.

Mild rashes from poisonous plants can be treated at home. These rashes cause discomfort due to itching, burning and blistering, but severe rashes that cover most of the body, require medical treatment.

Symptoms of an allergic reaction to a poisonous plant include an itchy or burning rash that appears within 2 to 3 days. The rash will first appear as small red bumps that usually blister. They may sometimes appear as straight lines or streaks on the child's skin and may begin to look crusty as they heal.

If your child comes in contact with poison ivy, you should:

  • Immediately wash the skin and scrub under the fingernails with soap and water. Put your child in the shower, rather than the bath because the oil from the plant can get into the bath water and spread to other parts of the body.
  • Use calamine lotion for itching (avoid using on face, especially near the eyes, or on the genitals) or give an oral antihistamine, such as Benadryl or Claritin.
  • Cut your child's fingernails short so that he or she does not break the skin when scratching.
  • Place cool compresses on your child's skin to soothe the pain.

• Wash all recently worn clothing, as well as any outdoor items that may have come into contact with the plant.Call your doctor if:

  • The rash covers a large part of the body or is on the genitals or face.
  • The skin is very red or warm; there is severe pain, swelling, or pus.

• The rash continues to get worse.Take your child to the emergency room if he or she:

  • Has a known severe allergy to poison ivy, oak or sumac.
  • Complains of tightness in his or her chest or has difficulty breathing.
  • Feels dizzy or lightheaded.
  • Has swelling around the nose or mouth.
  • Is hoarse or has trouble speaking.

• Has redness or swelling over most of the body.Learn to identify poison ivy, oak and sumac and teach your children what these plants look like and to stay away from them. Always dress your children in long-sleeved shirts and pants if they will be in areas where poison plants grow or avoid the areas.
Dr. Sally Robinson is a pediatrician in the division of children's special services at the University of Texas Medical Branch at Galveston. She teaches medical students about caring for children with chronic medical conditions. Dr. Keith Bly is a hospitalist and assistant professor of pediatrics at UTMB. This column is not intended to replace the advice of a physician.

The Your Health column is written by health and medical experts at the University of Texas Medical Branch at Galveston. The column focuses on topical health issues that we believe are of interest to your readers. It is e-mailed every Tuesday. If you have any questions about the column, or would like to suggest topics, please contact John Koloen, media relations specialist, at (409) 772-8790 or email