Healthcare
A Mozzie Repellent for Where You Are Going: Backyard, Campsite or the Tropics
NSW Health identifies three active ingredients as the most effective topical mosquito repellents: DEET, picaridin and oil of lemon eucalyptus. Repellents containing them are registered with the Australian Pesticides and Veterinary Medicines Authority, which NSW Health says checks that products are safe and effective, and the active ingredient is listed on the label. Within those conditions, the choice of product depends less on the brand than on three questions: where the repellent will be used, who will wear it, and for how long. The helper below works through those three questions and returns a plain summary drawn from NSW Health guidance. It is general information and not medical advice.
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What a mosquito repellent does
A repellent does not kill mosquitoes. NSW Health explains that it works by confusing the mosquito’s senses, so that the insect does not find the skin it would otherwise bite. That mechanism carries a condition that is easily overlooked: a repellent protects only the skin to which it has been applied. An uncovered ankle or a missed patch on the neck receives no protection from the product on the arms.
The method of application follows from this. NSW Health advises applying a thin, even layer to exposed skin, rather than misting it into the air around the body. Since the product protects only where it lands, the purpose of an even layer is to leave no exposed skin uncovered.
NSW Health also sets out what to avoid. Repellent should not be applied to the eyes, the mouth or broken skin. Where sunscreen is also needed, the order is sunscreen first and repellent second.
The three active ingredients
The three ingredients that NSW Health rates as most effective are DEET, picaridin and oil of lemon eucalyptus. The active ingredient, and its concentration, are listed on the product label, and the label is the document that governs how the product is to be used.
| DEET | Picaridin | Oil of lemon eucalyptus | |
|---|---|---|---|
| Rated by NSW Health among the most effective topical repellents | Yes | Yes | Yes |
| Product must be registered with the APVMA to be sold in Australia | Yes | Yes | Yes |
| Directions for age, quantity and reapplication | On the label | On the label | On the label |
The table is deliberately limited to what the authorities state. On the matters that people most often discuss when comparing these ingredients, such as how a product feels on the skin, how it smells, and how it interacts with clothing or equipment, this article makes no factual claim. Those are questions of personal preference, and a reader who has a preference on any of them may choose accordingly from among the three.
Oil of lemon eucalyptus should not be confused with eucalyptus oil in general. NSW Health lists eucalyptus among the natural repellents that provide very limited protection, while oil of lemon eucalyptus is among the three it rates most effective. The label states which is present.
Strength and time
NSW Health states that a higher concentration of active ingredient gives longer protection. The statement concerns duration: the relevant question for the buyer is how long the product must last before it can be reapplied, and the label is where the manufacturer states that period for the particular product.
Reapplication is governed by the label. NSW Health advises reapplying as the label directs, and more often where the person is sweating or after swimming, since both remove the product from the skin. A product chosen for a short evening in the backyard and a product chosen for a full day outdoors may therefore differ, not because one ingredient is superior, but because the second situation calls for protection that lasts longer between applications.
This article does not state particular concentrations or hours of protection, because those figures vary between registered products and are set out on each product’s label.
Choosing by setting
The setting determines how long a person will be exposed, at what time of day, and whether any disease risk is involved. NSW Health notes that mosquitoes are most active at dawn, at dusk and in the evening.
The backyard or a local park. For a short period outdoors at dusk, a registered repellent applied to exposed skin, in a thin and even layer, meets the need. The yard measures set out later in this article reduce the number of mosquitoes present in the first place.
A day walk, a campsite or the beach at dusk. For longer periods, NSW Health advises combining repellent with clothing. Long, loose and light-coloured clothing covers the skin that repellent would otherwise have to protect. A higher-strength product, reapplied as the label directs, suits a day outdoors. Those spending the warmer months in the bush should also be aware of the other hazards of the season, including brown snakes in spring.
Overnight outdoors. NSW Health travel advice recommends sleeping under a bed net, ideally one treated with permethrin, or in a screened or air-conditioned room. The treatment referred to here applies to the net, and this article gives no advice on applying permethrin to the skin.
Northern Australia and travel to the tropics. Some destinations carry a risk of mosquito-borne disease. NSW Health advises avoiding areas with known outbreaks. The question of disease risk is a medical one, and the appropriate course is to see a general practitioner or a travel doctor before departure and to read the Smartraveller advice for the destination. A traveller planning a trip to one of the eco-friendly destinations in the tropics should allow time for that appointment before the date of travel.
Children
NSW Health states that most repellents are safe for children aged three months and older when used as directed, and that some formulations are recommended only from 12 months. The label states which applies to a given product, and it should be read before the product is used on a child.
Responsibility for application rests with the adult. NSW Health advises that adults apply repellent to children rather than allowing children to apply it themselves. For a day out, that means applying it in the morning and again as the label directs.
For babies under three months, this article does not recommend a repellent. Physical protection is the appropriate measure: a fine net over the pram or cot, and light clothing that covers the arms and legs. Any question about using a repellent on a baby of that age is a question for a general practitioner.
What does not work
NSW Health is explicit that several products sold for mosquito protection do not provide effective protection. These include wristbands, patches, ultrasonic devices and phone applications. A person relying on any of them should not assume that they are protected.
NSW Health also states that natural repellents, such as citronella, eucalyptus and tea tree, provide very limited protection. They may be pleasant to use, but they should not be relied on in place of a registered product containing one of the three ingredients named above, particularly where disease risk is present.
Around the house
The most effective measure around the home is to remove the water in which mosquitoes breed. NSW Health sets out a series of steps, summarised here.
- Empty containers that collect water, along with bird baths and pet bowls.
- Fill the bases of pot plants with sand, so that water does not pool in them.
- Keep gutters clear, so that water drains rather than stands.
- Fit screens to windows.
These measures are the responsibility of the householder, and they reduce exposure for everyone in the house, including those too young to wear a repellent.
After a bite
For an ordinary bite, NSW Health advises washing the area, applying ice to reduce swelling, and using an antihistamine cream as the label directs.
Certain symptoms call for more. NSW Health advises that a person who develops a rash or flu-like symptoms after being bitten should see a doctor. In an emergency, call 000.
The label is the instruction
Each of the questions in this article returns, in the end, to the same document. NSW Health directs that approved products be used as the label states, and notes that the proven repellents are registered with the APVMA. The label therefore carries two kinds of information at once: the active ingredient that places the product among the three NSW Health rates most effective, and the directions on age and reapplication that govern its safe use. A reader who has chosen by setting, by age and by hours outdoors still has to confirm that the particular product in hand suits the person who will wear it.
The responsibility for that confirmation rests with the buyer, and for children with the adult applying it. A product that suits one member of a household may not suit another, and a product chosen for a backyard evening may not be the right one for a weekend under canvas.
The guidance in this article reduces to a set of conditions, each drawn from NSW Health and each applied through the product label.
- Choose a registered product containing DEET, picaridin or oil of lemon eucalyptus.
- Read the label for the ages the product suits and how often it must be reapplied.
- Apply sunscreen first and repellent second, in a thin and even layer, away from the eyes, the mouth and broken skin.
- Reapply sooner after sweating or swimming.
- For children, apply it yourself. For babies under three months, use nets and clothing, and ask a general practitioner.
- For travel to areas with mosquito-borne disease, see a doctor before departure and check Smartraveller.
- Do not rely on wristbands, patches, ultrasonic devices or phone applications.
A product chosen on these conditions, and used as its label directs, is the protection the authorities describe.
Sources: Mosquito borne diseases: Bite prevention, NSW Health (https://www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/bite-prevention.aspx)