Summer’s here and after a wet spring in many parts of Australia, mosquitoes are out in force. Insect repellent has become a routine requirement for time outdoors.

But how safe are they? And do we real­ly need them?

What can go wrong after a mosquito bite?

A bite from a mos­qui­to can be itchy and irri­tat­ing. Even a mild reac­tion can have us scratch­ing, espe­cial­ly if you’re one of the peo­ple who are irre­sistible to mos­qui­toes.

The swelling and itch­i­ness usu­al­ly resolves in a few days. But scratch­ing can result in sec­ondary infec­tion, espe­cial­ly for young chil­dren, if dirt and germs from under­neath the fin­ger­nails get into the sore.

A mos­qui­to bite can also cause dis­ease. Not all dis­eases are life-threat­en­ing but they can be severe­ly debilitating.

These dis­eases are a risk in most parts of Aus­tralia. Even cool­er regions such as Vic­to­ria and Tas­ma­nia have mos­qui­to-borne dis­eases which can be seri­ous­ly debilitating.

Stop the bite, stop getting sick

There are no spe­cif­ic cures for our local mos­qui­to-borne dis­eases. While there is a vac­cine avail­able for Japan­ese encephali­tis, pre­vent­ing bites in the first place is the best way to pre­vent ill­ness­es caused by Ross Riv­er, Mur­ray Val­ley encephali­tis and a range of oth­er pathogens spread by mos­qui­to bites.

Aus­tralian health author­i­ties reg­u­lar­ly review the rec­om­men­da­tions for insect repel­lent use. But the range of for­mu­la­tions fill­ing our super­mar­ket shelves can change from sum­mer to summer.

The Aus­tralian Pes­ti­cides and Vet­eri­nary Med­i­cines Author­i­ty (APVMA) assess­es insect repel­lents for their safe­ty and effec­tive­ness. Pack­ag­ing should clear­ly dis­play an APVMA reg­is­tra­tion num­ber, along with direc­tions for safe use and any required warn­ings, on their label.

What’s in popular mozzie repellents?

The most wide­ly avail­able active ingre­di­ents are diethyl­tolu­amide (DEET), picaridin and oil of lemon euca­lyp­tus (OLE).

Plant-derived prod­ucts, includ­ing euca­lyp­tus and tea tree oil, are also pop­u­lar alter­na­tives. These strong­ly smelling prod­ucts are reg­is­tered by the APVMA and pro­vide some pro­tec­tion but need to be reap­plied more fre­quent­ly than oth­er repellents.

Are mosquito repellents safe?

Insect repel­lents are often thought to be unpleas­ant to use, or even a health risk them­selves, but the incon­ve­nience of using a repel­lent is eas­i­ly out­weighed by the ben­e­fit of reduc­ing mos­qui­to bites.

Research and reviews from sci­en­tists and health author­i­ties show mos­qui­to repel­lents are a safe and effec­tive way to pre­vent mos­qui­to bites if used as recommended.

Sci­en­tists inves­ti­gate each active ingre­di­ent to deter­mine whether it’s safe. DEET has been the sub­ject of many stud­ies. Picaridin and oil of lemon euca­lyp­tus haven’t been used for as long and haven’t been as thor­ough­ly stud­ied as DEET, but remain among those rec­om­mend­ed by health author­i­ties in Aus­tralia and overseas.

Nat­ur­al repel­lents, espe­cial­ly unreg­is­tered and DIY for­mu­la­tions, may may cause skin reac­tions or come with oth­er risks, so stick with prod­ucts that have been reg­is­tered after being test­ed for safe­ty or effectiveness.

How­ev­er, even if a prod­uct has been deemed safe, it is impor­tant to fol­low the direc­tions for use on label. There will always be a risk if prod­ucts are ingest­ed in large quan­ti­ties or inten­tion­al­ly mis­used.

What about babies and young children?

Most mos­qui­to repel­lent for­mu­la­tions in Aus­tralia are reg­is­tered for use on chil­dren over 12 months of age, although not all for­mu­la­tions list a spe­cif­ic age restriction.

Inter­na­tion­al stud­ies have shown that DEET and picaridin are safe for chil­dren. Rec­om­mend­ed age lim­its for some mos­qui­to repel­lents vary between coun­tries and prod­uct type. In the Unit­ed States, for exam­ple, there is no age lim­it for the use of DEET, while oil of euca­lyp­tus is rec­om­mend­ed only for chil­dren over three.

A 2024 study review­ing reports of adverse out­comes from mos­qui­to repel­lent use con­clud­ed DEET was the pre­ferred insect repel­lent for chil­dren, as it was the safest and offered long-last­ing pro­tec­tion against bit­ing mos­qui­toes when used as direct­ed. The researchers not­ed oth­er active ingre­di­ents may pro­vide sim­i­lar pro­tec­tions but more assess­ments were required to deter­mine their safety.

Tips for parents of babies and young children

Always be guid­ed by the cur­rent rec­om­men­da­tions of the APVMA and lim­it the use of DEET-based repel­lent from 12 months. Check the label before using mos­qui­to repel­lent on children.

When you’re apply­ing repel­lent, ide­al­ly apply it to your hands, then rub it on their skin. If you’re using a spray, apply it care­ful­ly and nev­er direct­ly onto a child’s face.

Don’t allow chil­dren to apply their own repel­lent, as it may lead to acci­den­tal inges­tion or over-exposure.

When babies and tod­dlers are out­doors, con­sid­er using an insect net for strollers, prams or playpens.

While wrist bands, patch­es and stick­ers are mar­ket­ed as mos­qui­to repel­lents for chil­dren, there is lit­tle evi­dence they are effec­tive. Smoul­der­ing devices, such as coils and sticks, aren’t a good idea when there is a chance of breath­ing in the smoke.

How do different varieties compare?

Unlike sun­screens, which have a SPF rat­ing, there isn’t a sin­gle mea­sure with which to com­pare the dif­fer­ent for­mu­la­tions of mos­qui­to repel­lents and their effectiveness.

“Heavy duty” or “trop­i­cal strength” for­mu­la­tions often con­tain the same active ingre­di­ents as those known as “kid friend­ly”, but in high­er dos­es that last longer.
Low­er con­cen­tra­tions still offer good mos­qui­to bite pro­tec­tion, they just need to reap­plied more often.

The secret to get­ting the best pro­tec­tion is to ensure mos­qui­to repel­lents are applied cor­rect­ly. Whether you use a cream, lotion, gel, roll-on, pump-spray or aerosol, make sure all exposed skin is cov­ered. Reap­ply after swim­ming, sweaty exer­cise, or if it has rubbed off.

Cameron Webb, Clin­i­cal Asso­ciate Pro­fes­sor, School of Med­ical Sci­ence & Syd­ney Infec­tious Dis­eases Insti­tute; Prin­ci­pal Hos­pi­tal Sci­en­tist, Uni­ver­si­ty of Syd­ney and Med­ical Ento­mol­o­gist, NSW Health Pathology.

This arti­cle is repub­lished from The Con­ver­sa­tion under a Cre­ative Com­mons license. Read the orig­i­nal arti­cle.