Stinging plants

We are pretty familiar with insects and animals that bite and sting. The plant world also has a few unfriendly ways of arranging protection, with some making you itchy whilst others can leave you in pain for months. Soft-skinned walkers beware. It seems that Australia can boast that we have the most painful plant in the world, the Stinging Tree. Somehow this makes us a little proud….

Remember that it’s not just the living trees that sting, it’s dead leaves too. That means that if you spot a stinging plant, beware of leaf litter surrounding the area too.

Stinging trees are generally found in rainforest on the eastern parts of Australia. Australia has four common types: two that are large rainforest trees growing up to 30 to 35 m. The other two, only bushes often between 0.1 to 1m tall. All four species have a similar stinging mechanism but D. moroides (the Gympie Gympie) is generally considered to have the worst sting.

Gympie-gympie (Dendrocnide moroides)
Common names	stinging bush, gympie stinger, mulberry-leaved stinger, gympie gympie, gympie, stinger or moonlighter
Tree height	around 2 metres
Leaf size	large vaguely heart shaped leaves (about the size of your hand)
Link on Wiki	Gympie-gympie

Giant stinging tree (Dendrocnide excelsa)
Common names	Australian nettle tree, fibrewood, gimpi gimpi, giant stinging tree, gympie
Tree height	over 30 metres high
Leaf size	leaves are large and heart shaped with serated edges, however unlike the D. moroides, the D. excelsa’s leaves join the stalk at the notch between the overlapping lobes
Link on Wiki	Giant stinging tree
Location	found in rainforests in NSW and southern QLD

Shiny leaf stinging tree (Dendrocnide photinophylla)
Common names	fibrewood, small-leaved nettle, mulberry-leaved stinging tree, and gympie
Tree height	similar to the Giant stinging tree, but much narrower, up to 20 metres
Leaf size	leaves are glossy on the upper surface, long and narrow shaped (6-12 centimetres long) with wavy or sometimes toothed margins
Link on Wiki	Shiny leaf stinging tree
Location	found in rainforests on the east coast of Australia between Sydney to Cooktown

Atherton Tableland stinger (Dendrocnide cordata)
Common names	gympie, stinger
Tree height	up to 4 metres
Leaf size	heart shape leaves but with a broad notch at the base which is inserted the leaf stalk
Location	found on the Atherton Tablelands

As a general rule, if you are unsure or can’t remember the specific features of stinging trees, keep clear of plants with heart-shaped leaves with saw-toothed margins that look furry.

Other stinging plants are the ground-hugging nettles. They occur in many different environments, but particularly wet, shady areas.

How do they sting?
The leaves and some branches and fruits of Stinging Tees are covered in tiny hairs, hollow silica needles that range in length from 0.2 to 2 millimeters. They look deceptively soft and furry, yet they are effectively glass hypodermic needles. Do not touch!

Interestingly, it seems that the pain is not just because of the needles but due to the fact they carry a neurotoxin. According to an ABC article “One scientist, Oelrichs, purified the poison and injected himself with it and suffered intense pain. He proved that the toxin, not the silicon hairs, caused the pain. If you have stabbed yourself with the hairs, you can release the neurotoxin from the hairs by heating or cooling your skin, or just touching it. This neurotoxin is very stable. Experiments have been done with hairs that were collected nearly a century ago, and they can still cause pain.” This article goes on to point out two interesting facts. Firstly, that the tree seems to have no effect on most Australian native animals. Secondly, and more interestingly, is that the plant does not seem to do any actual damage to your body. Unlike the venom from a snake or spider that causes damage to your body in many ways, this toxin seems to “just” cause pain.

Signs and symptoms – how bad is the sting?
The sting of Stinging Trees is pretty bad! In fact, after being stung by a stinging plant the pain can recur for more than two months. And it’s not just the living leaves that sting, dead leaves too can cause problems.

“Stinging trees (Gympie-Gympie) are the bane of people in the Australian tropical and sub-tropical coastal areas – especially after disturbances such as cyclones, which trigger the germination of seeds. It becomes quite an issue when children wander into small plants – and are really badly stung.”

Poisonous plants of Australia by Selwyn Everist (1974) has 684 pages – a lot of poisonous plants. At page 515 he says the following about stinging plants: “If the leaves or the twigs make direct contact with the skin, the hollow, silica-tipped hairs penetrate and there is at first a slight itch, followed in a few seconds by a severe prickling effect which quickly becomes intense pain of a complex nature. The pain is described … as composed of a background of tingling on which is superimposed an intermittent stabbing pain with sharp radiations passing in all directions.” He goes on to say the pain lasts for around eight hours (maybe 30 hours). The pain then can continue to recur for more than two months. More recent research cited by the ABC suggests that the “The pain comes immediately after touching the plant, and it gradually increases to a peak after about 20-30 minutes”. On top of this, it seems that some people can be allergic to the sting and suffer life-threatening anaphylactic shock, although deaths are very very rare.

Prevention
So let’s not allow these plants stop us from heading bush. Avoid the need for first aid by learning to spot these plants and giving them the respect they deserve. They are part of the Australian native ecosystem and deserve their space. Oh, and make sure you always have enough toilet paper so there is no risk of grabbing a leaf from one of these trees by mistake.

• Know how to ID plants
• Protective clothing: When walking in some areas, body armour could help :), but since the trees generally grow in warmer areas this has limited practical application. Long thick pants, a shirt and a hat can help protect from brushing against the leaves. Wearing thick gardening gloves will also reduce the risk of getting stung if your hands grab a leave or branch. Just be aware through that the clothes and gloves may collect needles whilst you are walking – so be mindful of this when removing and handling the clothing.

Management
Always work through the standard DRSABCD protocol. Avoid anyone else getting stung.

For stinging trees
The federal government healthdirect website suggests that you follow these four points:

1. The most important thing is that you do not rub the area, as this can break off the hairs and make them very difficult to remove,
2. Remove visible hairs with tweezers,
3. Apply and remove adhesive tape or hair removal wax strip to the area to remove the finer hairs, and
4. Do not scratch or rub the area, this may cause the hairs to penetrate deeper into the skin.

This simple treatment was developed in the 1990’s by Dr.Hugh Spencer of the Australian Tropical Research Foundation (AUSTROP). Although the original recommendation is to use the sugar-based depilatory “Waxeeze”, which is readily available from most pharmacies, any wax strip-based depilatory will work.

The rationale is to remove the hairs without disturbing them. Remove the visible hairs manually and then remove the remaining smaller hairs using wax strips. If the wax isn’t pre-applied to the strips, then first spread it onto cloth or strips. Do not apply wax directly to the skin because it’s likely that the hairs will break, causing immense pain to the patient, and making them hard or impossible to remove.

The use of pain relieving medication may also help reduce the signs and symptoms.

In 2013, AUSTROP published their updated protocol to deal with stinging trees via a blog post. They have had positive that applying a dilute solution of hydrochloric acid soaked in a cloth on the affected area will help neutralise the proteins. This is reported to be very painful for around 5-10 minutes but “the pain and after-sensitivity is completely gone in about 12 hours after treatment (as opposed to waiting for 3-6 months!)”. Although this method has been the subject of several student studies, the research base for it is very limited, and we strongly suggest that you speak with your doctor before trying this or before adding any hydrochloric acid to your first aid kit.