Redhill hornet attack: What should I do if I’ve been stung multiple times and how venomous is it?

SINGAPORE – Four people were taken to hospital after a hornet attack near Redhill Market on July 10, the latest in a series of such incidents in Singapore in recent years.

An earlier incident in Sungei Buloh in 2024 resulted in five people being taken to hospital. Hornet attacks also killed one person each in 2022 and 2019.

The Straits Times looks at where hornets are commonly found in Singapore, the risks they pose and what to do if you are stung.

Where are hornets found in Singapore?

Hornets’ nests are most commonly built between 1m and 7m above ground, and may be constructed on trees, shrubs or man-made structures, according to a 2023 paper published in the Raffles Bulletin Of Zoology.

Nests have previously been spotted in the Central Catchment Nature Reserve and Upper Seletar Reservoir Park, according to the paper.

They can also be found near residential areas, according to information on pest control company Innovative Pest’s website. Prime nesting sites include balcony corners and window ledges, as well as the undersides of roof eaves.

The sheltered spaces around external air-conditioning units, compressors and service ducts also provide favourable nesting conditions. Inspect these areas regularly for early signs of nest-building, Innovative Pest advises.

Reducing outdoor lighting near potential nesting sites may also help, as hornets are attracted to brightly lit areas while hunting.

What happens when a person gets stung by a hornet?

The venom of Hymenoptera insects – such as hornets, bees and wasps – contains histamine, a chemical that triggers an allergic response, and melittin, which causes pain, said Jonathan Tang, senior consultant with National University Hospital’s Emergency Medicine Department, on the hospital’s health resources website.

The venom also contains proteins such as phospholipase and hyaluronidase, which can damage human cells.

Most people develop a mild local reaction, including pain, redness and swelling at the sting site, which usually resolves within 24 hours. Others may experience a large local reaction, with swelling exceeding 10cm that can take up to a week to subside.

In severe cases, symptoms may include low blood pressure, decreased blood flow to vital organs or airway swelling, which causes suffocation.

How dangerous is a hornet sting?

A hornet sting can be more dangerous than a bee or smaller wasp sting because hornets can sting multiple times, injecting a larger amount of venom with each sting, said Tang.

Furthermore, according to the National Parks Board (NParks), hornets are highly defensive of their colonies and may launch a mass attack if they perceive a threat.

If you encounter a hornets’ nest, leave it alone, says NParks, especially if it is in its natural habitat.

Avoid swatting at the insects or making sudden movements, as this may provoke them and trigger a more aggressive response.

Who is at risk of severe reactions? 

People who have previously had a severe allergic reaction to hornet or other Hymenoptera stings are at greater risk of developing a severe, potentially fatal allergic reaction known as anaphylaxis, said Tang.

People with pre-existing allergic conditions such as asthma are also at risk.

Those who sustain a large number of stings – typically more than 50 to 100 – are at risk of systemic envenomation, a toxic reaction caused by a large dose of venom.

Unlike anaphylaxis, which usually occurs soon after a sting, systemic envenomation has a delayed onset and may develop 24 to 48 hours later, potentially leading to multi-organ failure.

People with a history of severe allergic reactions to insect stings should carry an adrenaline auto-injector, such as an EpiPen, for emergency use, Tang said.

The elderly and those with underlying chronic lung and heart diseases, or those taking certain medications for high blood pressure or heart conditions, are also more susceptible to severe reactions from insect stings.

What should I do if I get stung?

If you are stung, move to a safe area immediately to avoid further attacks, said Tang. Do not attempt to suck out the venom, as this may cause further tissue damage.

Wash the affected area with soap and water, apply a cold pack to reduce swelling and take an antihistamine, if needed, to relieve itching. Paracetamol or ibuprofen may also ease pain and inflammation.

Seek immediate medical attention if you develop symptoms of anaphylaxis, such as swelling of the tongue or throat, difficulty breathing or dizziness, Tang said.

Anyone who has been stung more than three times should go to a hospital.