Why do nettles sting? And do dock leaves really help?

Stinging nettles can be a hazard on summer walks. I remember going on walks with my Dad when I was little and brushing my hands through the plants and getting stung. My dad immediately reached for a dock leaf to rub the stinging area. Then I was up and off on my way! But why do nettles sting? And did the dock leaf really help me?

Types of stinging nettle

Common nettle or stinging nettle (Urtica dioica)

This is the most common nettle found in Europe and is most likely the species of stinging nettle that comes to mind first. 

It can be identified by its green leaves with deeply serrated edges. It is often found as an understory plant in damp environments, but also in meadows, disturbed or enriched ground. The stems and underside of the leaves are covered in hollow hairs which can sting you.

Though we may think of the nettle as a pesky plant, it’s an important food source for wildlife, including:

• caterpillars of peacock, small tortoiseshell, red admiral and comma butterflies
• aphids and the ladybirds that feed on them
• chaffinches, bullfinches and sparrows
• hedgehogs, shrews, frogs and toad.

Scrub nettle or tall nettle (Urtica incisa)

This nettle is only found in Australia and New Zealand. It’s also referred to as stinging nettle and looks similar to the UK species.

Western nettle or western stinging nettle (Hesperocnide tenella)

Found in California, this nettle has a similar appearance to the other nettle species, though the tiny hairs on its leaves are hook-shaped.

Why do nettles sting?

The nettle’s sting is an adaptation to provide protection from predators. The sting causes any predator that may eat the plant or uproot it to stay clear.

Do dock leaves help nettle stings?

Dock leaves come from the genus Rumex and there are several species. The most common one in the UK is the broadleaved dock. It is characterised by its large oval leaves that have rounded tips. Some of the stems and leaves may have a reddish hue. It can be found in similar places to nettles, like meadows and damp understorey areas.

Dock leaves don’t just relieve stings – they’re also a food plant for the small copper butterfly.

There are a few theories as to why dock leaves appear to help nettle stings. The most plausible are:

• the cooling sensation of the sap evaporating from the affected skin can relieve some of the stinging sensation
• it could be merely a placebo effect. The belief that dock leaves help nettle sting is such a wide and popular opinion - maybe it works because people believe it works!

Whichever of these is true, if you are stung by a nettle, it’s definitely worth grabbing the nearest dock leaf and giving it a try!