Of all the invasive weeds we deal with, giant hogweed is the one that can genuinely hurt you. Its sap can cause painful, blistering burns, and because children are often drawn to its size and hollow stems, it pays to know how to recognise it and what to do if you come into contact with it.
Why giant hogweed is dangerous
The sap of giant hogweed contains chemicals that make skin extremely sensitive to sunlight. If sap gets onto your skin and that skin is then exposed to daylight, it can trigger a severe reaction known as phytophotodermatitis, causing redness, burning and large blisters. The affected skin can remain sensitive to sunlight for years afterwards, and reactions can flare up again.
How to identify it
Giant hogweed lives up to its name. Mature plants can reach three to five metres tall. Look for thick, green stems with purple blotches and stiff white bristles, large jagged leaves that can be over a metre wide, and enormous flat-topped clusters of small white flowers, like a vast cow parsley. It is often found along riverbanks, footpaths and waste ground. Our giant hogweed FAQ has more detail.
What to do if sap touches your skin
Act quickly. Cover the affected area to keep it out of sunlight, then wash it thoroughly with soap and cool water as soon as you can. Keep the skin shielded from daylight for at least 48 hours. Avoid touching your eyes or face. If you develop blisters, feel unwell, or sap gets into your eyes, seek medical advice promptly. For children, it is always worth a precautionary call to your GP or NHS 111.
Do not strim or cut it
Strimming giant hogweed is one of the worst things you can do, as it sprays sap over a wide area. Controlling it safely is a job for trained professionals with the right protective equipment.
Get expert help
If you have spotted giant hogweed on your land, keep people and pets away from it and contact us. Send a photo through our free weed checker from a safe distance, or call 07518 456090.
This article is general guidance and not a substitute for professional medical advice. If you are concerned about a burn or reaction, please contact a healthcare professional.
