Stinging nettles

Nettles are plants with sharp hairs on their leaves. If you touch them, these hairs inject irritants into the skin, making it itchy, red and swollen.

Summary

Stinging nettle is a common weed. It’s found in gardens, waste areas, near where animals live, and around moist areas such as creeks.

In New Zealand there are 3 species: the native ongaonga (giant tree nettle), and 2 introduced varieties.

Photo of an ongaonga or giant tree nettle. It has serrated green leaves with sharp white hairs sticking out from the middle of the leaf, and from the tip of each serration.
Photo of ongaonga (giant tree nettle), by Avenue.
Photo of introduced nettle Urtica dioica, which has rounded green leaves with soft serrated edges.
Photo of introduced nettle Urtica dioica, by Michael Gasperl / CC BY 3.0.
Photo of introduced nettle Urtica urens, which has sharp white hairs growing from the stalk of the plant.
Photo of introduced nettle Urtica urens, by Phil Bendle / CC BY-NC-ND 3.0.

 

Symptoms

Small exposures to nettles can cause local symptoms such as burning, itching, redness, swelling (occasionally small blisters will form) and local numbness. Symptoms are usually self-limiting and resolve within a few days.

In cases where a large area of the body has been exposed to the nettles, or you have been exposed to the nettles for a longer period of time it is possible further symptoms such as inco-ordination, tremor, muscle weakness and faintness may occur.

Treatment

Self-care for nettle stings

  • Wash the area with soap and water as soon as possible to relieve the sting and remove the nettle hairs. If no water is available, clean the area with a cloth or other available material
  • Local symptoms of pain and itching can be relieved by applying a moistened cloth and/or ice pack to the area. It is also important to refrain from scratching or rubbing the itchy areas
  • Antihistamines may be effective in relieving local itching and swelling, while creams such as hydrocortisone containing creams can help reduce inflammation. These are available at your local pharmacy
  • Use cool, light, bedding and clothing as this will also help relieve itching
  • Avoid extreme heat- have lukewarm baths and showers.

The National Poisons Centre is available 24 hours a day on 0800 764 766 for advice on first aid and treatment of stings.

Medicine precautions

  1. Do not give aspirin (acetylsalicylic acid) or aspirin-containing products to anyone 18 years or younger because of the risk of a serious illness called Reye’s syndrome.
  2. Take non-steroidal anti-inflammatory drugs (NSAIDs) with food or milk to prevent stomach irritation. Do not give NSAIDs to anyone with:
    • NSAID-induced asthma
    • increased risk of bleeding, such as ulcer disease, a bleeding disorder, if taking blood thinners (anticoagulants), or following surgery, significant trauma or major dental work
    • an allergy to NSAIDs.

When to see a doctor

While most nettle stings require no further treatment, seek immediate medical attention if you develop:

  • Loss of co-ordination
  • Faintness
  • Tremor
  • Muscle weakness
  • Breathing problems
  • Swelling under the skin
  • Abdominal pain

You should also seek medical attention if there is significant skin itching or rash that is not resolving with self care.

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