Photodermatitis is One of Four Types of Dermatitis Plants

Giant Hogweed is one that looks so lovely but beware especially in good weather.

Lee-Anne Hancock
3 min readAug 11, 2022


Photo by Aleksey Milov on Unsplash

The Giant Hogweed is a perennial plant and surprisingly part of the carrot family. This plant migrated from Europe to Canada and the United States. It is an invasive species.

The plant is federally listed as a noxious weed in many US states. Importing into the United States or moving it interstate without a permit from the Department of Agriculture is illegal.

The sap of the giant hogweed plant is phototoxic. Because of its phototoxicity and invasive nature, giant hogweed is often actively removed. In Southwestern BC, it is considered a hazardous plant that seriously threatens human health and our natural ecosystem.

It’s a huge plant, growing from five feet up to 16 feet, with three feet-wide, umbrella-like clusters of small white flowers. Leaves can be up to 15 feet wide, with rough and serrated edges, like a jagged saw. They are most likely found around areas with moist soil, including vacant lots, natural areas, riverbanks, roadways, and residential properties.

Toxic Dose

Giant hogweed sap contains furanocoumarins such as psoralen, methoxypsoralens, and bergapten which absorb specific wavelengths of UV light from the sun. Moist skin or high humidity increases the severity of the response.

One can find this toxic sap in the leaves, stems, flowers, and the root of giant hogweed. The contact can occur by brushing against broken parts, handling plant material, or even touching tools or mowing equipment used for giant hogweed control.


Painful and sometimes severe lesions may appear up to 48 hours after the skin comes into contact with the giant hogweed sap.

Heat and moisture can worsen the skin reaction. The sap doesn’t allow your skin to protect itself against sunlight. This toxic reaction can begin 15 minutes after contact, with peak sensitivity between 30 minutes and two hours after contact.


When the sap touches the skin, and there’s moisture, even sweat, one can see burning pain, swelling…



Lee-Anne Hancock

Retired Poison Control Specialist. Now writing murder mysteries and blogging about life, family, and the fun of retirement.