Cow parsley (Anthriscus sylvestris) is a widespread plant often seen in hedgerows and along roadsides. While generally considered to have mild effects, direct contact with its sap can lead to skin irritation for some individuals.
Understanding Cow Parsley’s Skin Effects
Cow parsley contains natural compounds called furanocoumarins, which are phototoxic. These compounds can cause a skin reaction known as phytophotodermatitis when skin that has come into contact with the plant sap is subsequently exposed to sunlight. This is not an allergic reaction, but rather a chemical one.
Symptoms of phytophotodermatitis develop hours after exposure, peaking within 24 to 72 hours. The reaction can include redness, itching, a burning sensation, and blistering on the affected skin. As blisters heal, hyperpigmentation may occur, causing skin darkening that can last for weeks or months. The severity of the reaction depends on factors such as individual sensitivity, the amount of sap on the skin, and the duration and intensity of sun exposure.
Identifying Cow Parsley
Cow parsley is a tall, herbaceous plant, growing up to 1.7 meters (5.5 feet) in height. Its stems are hollow, grooved, typically green with occasional purplish tints, and covered with fine, rough hairs. Leaves are fresh green, fern-like, deeply divided, and arranged alternately.
The plant features umbrella-like clusters of small, delicate white flowers (umbels), typically 6 centimeters (2.4 inches) in diameter. Flowers usually appear between April and June, making it one of the earliest umbellifers to bloom. It commonly thrives in shaded habitats like woodland edges, hedgerows, roadside verges, and meadows.
Immediate Steps After Contact
If skin contact occurs, wash the affected area thoroughly with soap and cold water immediately. After washing, keep the exposed skin out of direct sunlight for at least 48 hours to prevent or minimize a reaction. Covering the area with clothing helps protect it from further sun exposure.
Medical attention may be necessary for severe symptoms, such as large blisters or signs of infection like oozing sores. If sap gets into the eyes, rinse with cold water and seek medical help promptly. The affected skin might remain sensitive to sunlight, so continued sun protection is advisable.
Distinguishing From Highly Toxic Lookalikes
Cow parsley is often confused with other plants in the Apiaceae (carrot) family, some of which are highly toxic, including Giant Hogweed and Hemlock. Accurate identification is important to prevent serious harm.
Giant Hogweed
Giant Hogweed (Heracleum mantegazzianum) is significantly larger than cow parsley, capable of growing up to 3 to 5 meters (10 to 16 feet) tall, with flower heads that can reach up to 1 meter (3 feet) across. Its stems are thick, hollow, and typically have distinct purple blotches and coarse, stiff bristles, unlike the finer hairs and greener stems of cow parsley. Giant Hogweed sap is highly phototoxic and can cause severe burns, blisters, and long-lasting scars, with the affected skin remaining sensitive to sunlight for years.
Hemlock
Hemlock (Conium maculatum) also resembles cow parsley but can be differentiated by several key features. Hemlock stems are smooth, hairless, and often marked with distinctive purple spots or streaks, which are absent on cow parsley stems. Hemlock leaves are finely divided and fern-like, but the plant itself has an unpleasant, “mousy” odor, especially when its foliage is crushed, in contrast to cow parsley’s mild, parsley-like scent. All parts of the hemlock plant are highly poisonous and can be fatal if ingested, containing toxic alkaloids that affect the nervous system.