Poisonous Plants / Photodermatitis

There are dozens of plants that contain rash-inducing chemicals, including members of the celery, rue, mulberry, pea, and aster families. The human reaction to these chemicals (called furanocoumarins) is generally mild. Common plants, such as sunflowers, wild grapes, and clematis can also be irritating to touch.

Other plant toxins can cause itchy rashes and painful boils. To protect yourself, take the time to learn to identify some poisonous plants and wear proper clothing to protect yourself from any contact.

Wear protective clothing: long-sleeved shirt, socks, and closed-toe shoes.

  • Cover all exposed skin.
  • Wash clothes and skin with soap and water after an exposure.
  • Wear work gloves and wash them regularly.



Photodermatitis, sometimes referred to as sun poisoning or photoallergy, is a form of allergic contact dermatitis in which the allergen must be activated by light to sensitize the allergic response, and to cause a rash or other systemic effects on subsequent exposure.

Photodermatitis may result in swelling, a burning sensation, a red itchy rash sometimes resembling small blisters, and peeling of the skin. Nausea may also occur. There may also be blotches where the itching may persist for long periods of time. Two common plants commonly found in Vermont can react with sunlight to cause photodermititis are discussed below.

Posion Ivy

Poison Ivy

Some plants, such as poison ivy, can cause a rash to those who are allergic. The rash is caused by contact with urushiol, an oil found in poison ivy, poison oak, or sumac.

The oil is present in all parts of the plants, including the leaves, stems, flowers, berries, and roots. Indirect contact with urushiol can also cause the rash. This may happen when you touch clothing, a pet who has it on their fur, gardening tools, or other objects that have come in contact with the plant.

Note: NEVER burn poison ivy! The smoke contains particles that can cause serious injury to the eyes, skin, and respiratory tract.

wild parsnip

Wild Parsnip

Wild Parsnip grows wild along roadsides and other unmaintained areas, and produce yellow flowers that appear similar to Queen Anne’s Lace. Wild parsnip sap is different from the toxin found in poison ivy or poison sumac; the reaction your body has to it has nothing to do with your immune system, and everyone is susceptible. The harmful chemical compounds are photosensitizing. This means they are activated by UV radiation from the sun.

Furocoumarin is the chemical in wild parsnip that causes this plant to react with sunlight and damage skin. When absorbed by skin, furocoumarins are energized by ultraviolet light (present during sunny and cloudy days) causing them to bind with nuclear DNA and cell membranes. It can destroy cells and skin tissue. This reaction, however, takes time to produce visible damage.

Wild Chervil

Wild Chervil

Wild Chervil

Wild Chervil, Anthriscus sylvestris (L.) Hoffm., is a weed belonging to the parsley family (Apiaceae) and is becoming a serious problem in hay fields and pastures in central Vermont. It's three to four foot heights, fern-like leaves and white flowers arranged in a compound umbel pattern are quite pronounced during late May to early July and are commonly found along roadsides and in meadows in central Vermont.

Wild Chervil is very difficult to control because of its extremely deep taproot and its resistance to herbicides. Wild Chervil sap can cause a chemical burn on skin when it is exposed to sunlight. This creates an additional hazard to anyone mowing, weed-whacking or walking in it.


There are other plants that can cause allergic reactions or chemical irritations. Be aware of your surroundings and protect yourself as best you can, especially when removing invasive species or working in brushy areas.