Insect repellents

How to use insect repellents safely

Easy-to-read information about insect repellents – what they are, how to use them safely and possible side effects.

Insect repellents are applied on your skin and clothes to keep away (repel) insects. They can help protect you from biting insects like mosquitoes and sandflies. This is especially important for travellers visiting countries where mosquitoes spread diseases such as malaria, dengue fever, Zika and yellow fever.

How do mosquito repellents work?

Mosquitoes are attracted to skin odours and the carbon dioxide we exhale. They also use heat, movement and visual cues to find a possible host. Repellents create a barrier that affects an insect's senses, such as smell and taste, to prevent it from finding a human host.

Types of insect repellents

There are a variety of insect repellents available in New Zealand. They are available in different forms, such as a spray, stick, roll-on, cream or gel, which are applied to your skin. Check the active ingredient in the insect repellent you are buying, as not all have been proven to work. Insect repellents containing the following active ingredients provide reasonably long-lasting protection:

  • diethyltoluamide (DEET)
  • picaridin (also known as icaridin)
  • IR3535
  • oil of lemon eucalyptus (also known as OLE or PMD).

Also check the strength of the ingredient it contains. This is usually described as a percentage (%). Repellents containing 20–50% DEET are recommended (use a maximum of 30% DEET for children). High concentrations of DEET protect for longer, but there is no additional benefit to using products with more than 50% DEET. Other products containing 20–25% picaridin and those containing about 30% oil of lemon eucalyptus can also be used.

Sweat, water contact and rubbing from clothing can affect how long a repellent may be effective. Water resistant repellents are available.

There are some insect repellents made from a blend of herbs and essential oils such as citronella, lavender, lemongrass, rosemary, tea tree, eucalyptus and peppermint. These generally have a weaker or shorter-lived repellent effect. They may be more suitable where there is no risk of exposure to mosquito-borne diseases.

Insect repellents in babies and children

Where possible, avoid exposing your baby or child to mosquitoes. Consider staying indoors, using pram netting or dressing them in loose long-sleeved clothing, socks and shoes. Before using an insect repellent on your baby or child, check that it is suitable for their age. The following is a guide:

  • DEET: Not recommended for babies younger than 2 months.
  • Picaridin: Not recommended for children younger than 2 years.
  • IR3535: Not recommended for babies younger than 6 months.
  • Oil of lemon eucalyptus: Not recommended for children younger than 3 years.

It's important to apply insect repellents correctly. See using insect repellents correctly below.

Insect repellents in pregnancy and breastfeeding

Insect repellents containing DEET, picaridin, oil of lemon eucalyptus (OLE), or IR3535 can be used by pregnant or breastfeeding women when used according to the product label.5

Using insect repellents and sunscreen

If you need to use repellent and sunscreen together, it is best to apply the sunscreen first, let it dry and then apply insect repellent over the sunscreen. Sunscreen does not affect repellent effectiveness, but the repellent may decrease sunscreen effectiveness. You may need to reapply sunscreen more frequently and in larger amounts. 

Using certain types of sunscreen and repellent together can increase the amount of repellent absorbed through the skin. Combined sunscreen and repellent products are available but not generally recommended. This is because repellent action usually lasts for several hours, whereas sunscreen may need to be reapplied more frequently.

Using insect repellents correctly

Use insect repellents correctly to get the most benefit and reduce your risk of harm.

Where to apply

  • Apply repellent only to exposed skin or clothing. Do not apply repellent underneath clothing. This can increase the amount of repellent that is absorbed into your skin.
  • Do not apply repellent to wounds, open cuts, irritated or sunburned skin, eyes or mouth.

How much to use 

  • Follow the instructions on the label and do not exceed the recommended application frequency. Avoid applying too much repellent and too often. Apply just enough of a repellent to cover exposed skin. Using excessive amounts does not make it more effective. If biting insects do not respond to a thin film of repellent, apply a bit more.
  • If you are outdoors for long periods or doing activities that cause profuse sweating, you may need to reapply repellent. Follow label directions to find out how long to wait before reapplying. Repellents do wash off in water, so if you are doing water activities, use a water resistant repellent or re-apply as mentioned in the directions for use.

Using a spray 

  • If using a spray, do not spray repellent on your face, in your ears or near your eyes or mouth. To apply a spray repellent to your face, first apply it to your hands and then rub it onto your face. 

Babies and children

  • Before using an insect repellent on your baby or child, check that it is suitable for their age (see above).
  • Children under 10 years should not apply their own repellent. Instead, adults should apply it to their own hands first and then gently spread on your child’s exposed skin.  
  • To avoid potential ingestion during eating, do not apply repellent to the hands, fingers or palms of young children.

Wash after use

  • Wash your hands after application to avoid accidentally putting repellent in your eyes. 
  • After returning indoors, wash repellent-treated skin with soap and water, or bathe. Likewise, after returning indoors, wash children’s treated skin and clothing with soap and water or give the child a bath. 

Insect repellent used on clothing

You can apply DEET or other regular insect repellent directly onto clothing, but this then has to be reapplied at regular intervals the same as when you use it on skin. 

Permethrin can be applied to clothing, hats, shoes, bed nets, jackets and camping gear for added protection. Examples of available products to do this with include Sawyer Permethrin Clothing Insect Repellent® and Repel Permethrin Treatment Kit For Fabric®. Clothing and other items must be treated 24–48 hours in advance of travel to allow them to dry. 

Alternatively, clothing can be bought pretreated with permethrin. Permethrin-treated materials retain their ability to repel or kill insects after repeated washes. Check the label for the number of washes that the repellent lasts for.  

Possible side effects

When used as directed, side effects due to insect repellents are rare. They can cause skin irritation, eye irritation and headache. If you get a rash or itching from an insect repellent, wash off the product using mild soap and water and discontinue its use.

Learn more

The following links have more information on insect repellents. Be aware that websites from other countries may have information that differs from New Zealand recommendations.

Insect repellents – guidelines for safe use The Royal Children's Hospital, Melbourne, Australia
Insect repellents help prevent malaria and other diseases spread by mosquitoes CDC, USA
Mosquito repellents University of Florida, USA 

References

  1. Avoiding bug bites while travelling Ministry of Health, New Zealand 
  2. Insect repellents National Pesticide Information Centre
  3. Efficacy of insect repellents currently available in New Zealand ESR, New Zealand  
  4. Mosquitoes, ticks and other arthropods Yellow Book, CDC, USA
  5. Zika virus Ministry of health, New Zealand
Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr Li-Wern Yim, Travel Doctor Last reviewed: 02 Oct 2019