Version July 2025
INTRODUCTION —
Tools for prevention of arthropod bites, including efficacy and safety of available repellents and permethrin-treated clothing, will be reviewed here.
Other tools for preventing mosquito bites include use of insecticide-treated nets, as well as housing and environmental modifications; these are discussed separately. (See "Malaria: Epidemiology, prevention, and elimination", section on 'Vector control'.)
Issues related to chemoprophylaxis for malaria prevention are discussed separately. (See "Prevention of malaria infection in travelers".)
PREVENTION GOALS —
Goals for prevention of arthropod bites include [1]:
●Reducing the risk of arthropod-borne infections (such as malaria, dengue fever, Zika virus infection, yellow fever, and others).
●Avoiding the nuisance of biting arthropods, including itching and local bite reactions.
OUR APPROACH
Preventing mosquito bites
●Use of repellent and permethrin-treated clothing – The approach to repellent use depends on the risk of disease associated with mosquito exposure and perceived intolerance to being bitten [2,3]:
•In regions with high risk of mosquito-borne disease transmission (such as in malaria-endemic areas), our approach to mosquito bite prevention consists of applying topical DEET (N,N-diethyl-3-methylbenzamide; 10 to 35 percent) to exposed skin, combined with use of permethrin-treated clothing.
Microencapsulated DEET formulations (such as Ultrathon [brand name], a 34 percent DEET lotion) provide longer duration of protection with lower repellent concentrations.
Use of topical picaridin (up to 30 percent) is a reasonable alternative to topical DEET for individuals who wish to avoid the unpleasant characteristics of DEET and are willing to accept a potentially less effective or shorter-acting repellent.
•In areas with low risk of mosquito-borne disease transmission, for patients who wish to avoid nuisance bites, reasonable approaches include applying topical repellent (DEET or picaridin), with optional use of permethrin-treated clothing.
●Behavioral interventions – Interventions to reduce the risk of mosquito bites include:
•Modifying activities to avoid mosquito bites; measures might include staying indoors at dawn and dusk and avoidance of wetland areas.
•Eliminating standing water in the immediate environment to reduce mosquito breeding areas.
•Maintaining screens on windows and doors.
Preventing tick bites — Tools for tick bite prevention include [4,5]:
●Use of repellent and permethrin treated clothing – For prevention of tick bites, we suggest application of topical repellent (DEET or picaridin) to exposed skin, combined with use of permethrin-treated clothing. Use of permethrin-treated clothing is important because ticks commonly gain access to areas of skin where topical repellents are not applied.
Microencapsulated DEET formulations (such as Ultrathon [brand name], a 34 percent DEET lotion) provide longer duration of protection with lower repellent concentrations.
●Behavioral interventions – Interventions to reduce the risk of tick bites include:
•Dressing to minimize tick access to the skin (tucking pant legs into socks and shirt into pants).
•Inspecting the skin after time spent outdoors, paying special attention to armpits, knees, navel, beneath underwear, and around the hairline of the neck and ears.
•Ticks attached to the skin should be removed promptly. (See "Evaluation of a tick bite for possible Lyme disease", section on 'Technique for tick removal'.)
Issues related to tick bite prevention are discussed further separately. (See "Prevention of Lyme disease".)
Application technique — Insect repellents should be applied to maximize effectiveness and minimize adverse effects [6].
●Apply sunscreen before repellent. Use separate sunscreen and repellent products; sunscreen requires more frequent reapplication than repellent.
●Apply repellent to exposed skin, clothing, or both; do not apply under clothing.
●Use repellent over intact skin only; do not use over wounds or over skin that is inflamed, sunburned, or eczematous.
●Use just enough repellent to lightly cover but not saturate the skin.
●For application to the face, dispense repellent into the palms and rub hands together, then apply a thin layer to the face.
●Do not apply repellent to children's hands; adults should dispense repellent into their own hands, then spread it on the child's exposed skin [7].
●After application, wash repellent from hands to prevent contact with mouth, eyes, and genitals.
●Once repellent is no longer needed, wash treated areas with soap and water.
●Do not inhale aerosols or get aerosols into eyes; do not spray aerosols near food or in enclosed spaces.
TOPICAL REPELLENTS
Spectrum of activity — Repellents are variably useful in deterring mosquitoes, biting flies, fleas, midges, chiggers, and ticks [3].
Repellants are not useful for deterring arthropods that bite or sting in self-defense; these include bees, wasps, ants, spiders, centipedes, and others. They are also not for preventing bedbug bites.
Repellents are most effective in areas where vectors feed in the early evening (as with many South American and Asian vectors), rather than later in the night (as with African vectors such as Anopheles gambiae).
Repellents may be more effective in regions with zoophilic vectors (as in the Americas and South Asia – where mosquitoes may be diverted from a repellent-treated person to an animal) than in regions with anthropophilic vectors (eg, Africa).
Arthropods are attracted to humans by body heat, odors on the skin, vibrations, and carbon dioxide. The active ingredients in repellents help ward off arthropods but do not kill them.
Preferred agents — N,N-diethyl-3-methylbenzamide (DEET) is considered the "gold standard" of insect repellents; it has been in use since the 1950s and provides the longest duration of protection [8-11]. Picaridin is a reasonable alternative for individuals who wish to avoid the unpleasant characteristics of DEET and are willing to accept a potentially less effective or shorter-acting repellent.
N,N-diethyl-3-methylbenzamide (DEET) — DEET has activity against mosquitoes, ticks, biting flies, chiggers, fleas, midges, and sand flies [8,11,12].
●Duration of protection – DEET is available in concentrations ranging from <10 percent to >75 percent [13].
•Mosquitoes – DEET (10 percent concentration) is effective for approximately two hours; DEET (24 percent concentration) is effective for approximately five hours [8].
Products with 10 to 35 percent DEET are adequate in most circumstances. Higher concentrations should be reserved for situations in which insect infestation is high or time outdoors will exceed three to four hours.
Microencapsulated formulations (such as Ultrathon [brand name], a 34 percent DEET lotion) increase the duration of protection while reducing skin absorption [14].
The efficacy of DEET plateaus at approximately 50 percent concentration; higher concentrations may provide longer duration of protection, but are associated with increased risk of skin irritation [2]. The duration of protection is shortened by swimming, washing, sweating, wiping, exercise, and rain [13,15].
•Ticks – DEET provides protection against ticks at higher concentrations than used for mosquitoes [13,16]. For this reason, we do not rely exclusively on DEET for protection against ticks; topical repellents should be used in conjunction with permethrin-treated clothing for optimal protection, especially since ticks commonly gain access to areas underneath clothing where topical repellents are not applied. (See 'Permethrin-treated clothing' below.)
●Use in children – In children, adverse neurologic effects (eg, encephalopathy) have been reported in the setting of inappropriate use (oral ingestion or repeated exposure to high concentrations) [11,17]. Hypersensitivity pneumonitis in a child following the inhalation of a DEET-containing insect repellent has also been described [18].
Recommendations regarding specific age thresholds for using DEET in children vary:
•In the United States, health and regulatory authorities (including the American Academy of Pediatrics, Environmental Protection Agency, and Centers for Disease Control and Prevention) consider DEET to be safe for children of all ages when used as directed [7,19-21]; prior guidelines supported the use of 10 percent DEET for children ≥2 months of age [22,23].
•In contrast, Canadian authorities (Canadian Pediatric Society, Health Canada) suggest that DEET not be applied to infants <6 months of age; alternatively, these groups suggest use of a mosquito net when outdoors [24].
●Use in pregnancy – Guidance for use of DEET in pregnant and lactating patients does not differ from that for nonpregnant adults [19,25,26].
In a randomized trial of insect repellents for malaria prevention among 897 pregnant patients, no adverse neurologic, gastrointestinal, or dermatologic effects were observed among the women or their infants [27].
There are no human data for first-trimester exposure. First-trimester exposure in rats and rabbits did not result in an increased risk of malformations in offspring [28].
●Adverse effects – Serious adverse reactions to DEET are uncommon.
•DEET can produce an oily, sticky skin sensation. Excessive skin absorption can cause dermatitis, allergic reactions, and rare neurotoxicity [29].
•DEET may reduce the efficacy of sunscreens applied simultaneously.
•DEET can damage some plastics and items made from synthetic fibers. It may dissolve mosquito nets, spandex, rayon, and leather, as well as plastic eyeglass frames and watches.
•Adverse effects in children are discussed above.
Picaridin (KBR 3023) — Picaridin, a plant-derived piperidine compound, has activity against mosquitoes, ticks, and the phlebotomine sand fly [30-34].
●Duration of protection
•Mosquitoes – For protection against mosquitoes, the efficacy of picaridin appears comparable to lower concentrations of DEET (≤30 percent) in many circumstances. However, higher concentrations of DEET (>50 percent) provide more effective protection than picaridin [35].
•Ticks – For protection against ticks, a trial comparing picaridin (20 percent) with DEET (20 percent) demonstrated efficacy for one hour and two hours, respectively [33].
Because ticks commonly gain access to areas of skin where topical repellents are not applied, particularly underneath clothing, topical repellents should be used in conjunction with permethrin-treated clothing for optimal protection. (See 'Permethrin-treated clothing' below.)
●Adverse effects
•Picaridin is odorless and leaves no residue. It does not irritate skin, stain fabrics, or degrade plastics.
•No toxicity in humans has been reported [7]. Accidental ingestions do not cause serious harm [36].
•No studies in human pregnancy have been published; based on available data, picaridin is unlikely to cause problems in pregnancy if used correctly. No developmental or reproductive toxicity has been observed in animal studies [37].
Alternative agents — Repellents that may be adequate in lower risk settings include oil of lemon eucalyptus (PMD), ethyl butylacetylaminopropionate (IR3535), and BioUD (2-undecanone); however, these agents are less well studied.
PMD — PMD (chemical name: para-menthane-3,8-diol, the synthesized version of oil of lemon eucalyptus) is the active ingredient in oil of lemon eucalyptus. PMD has activity against mosquitoes, biting flies, and gnats [38].
●Duration of protection – Studies of efficacy are limited and have yielded inconsistent results [39,40]. Some data suggest a PMD concentration of 30 to 40 percent may be effective for approximately four to five hours [41,42].
●Adverse effects – Adverse effects include skin and eye irritation; neither is common [43]. PMD has not been adequately tested in children <3 years of age and should not be used in this group [4].
IR3535 — IR3535 is a synthetic mosquito repellent.
There are limited studies comparing IR3535 with DEET or picaridin [32,44,45]. In one study, IR3535 appeared to be the least effective of the three repellents, although in another study, IR3535 compared favorably with DEET [32,45].
IR3535 should not be relied upon in malaria-endemic areas [46].
BioUD (2-undecanone) — BioUD is a tomato-derived mosquito repellent.
Efficacy data are limited; in one report comparing BioUD (7.75 percent concentration) with DEET (25 and 30 percent), the repellency of BioUD was comparable to that of DEET [47].
Agents with minimal or no effectiveness — Other agents marketed as insect repellents include citronella, various botanical oils, vitamin supplements, and herbal preparations.
●Citronella – Citronella is a plant-based repellent that lacks the broad spectrum of activity and duration of action of DEET [8,11]. Frequent application may compensate for its limited duration of effectiveness; however, in animal studies, citronella-based repellents have been shown to be potential dermal sensitizers [8]. Citronella probably is not effective in repelling ticks.
●Botanical oils – Various botanical oils, including cinnamon, peppermint, sandalwood, geranium, and soybean, have been used alone or in combination for repelling mosquitoes and ticks [48]. Most studies evaluating these plant-based repellents formulated into commercial products have shown that they provide inferior protection compared with DEET, picaridin, or PMD [44,49,50].
●Oral agents – Claims that ingestion of strong-smelling foods or other substances can repel biting insects (such as garlic, onions, cruciferous vegetables, or mineral sulfur) have not been substantiated.
●Vitamin supplements or herbal remedies – No scientific study of ingested vitamins or herbal remedies has shown these interventions to protect from biting insects [51].
●Repellent bracelets – Bracelets and wristbands impregnated with insect repellents are not effective [8,52].
●Electronic devices – Electronic devices emit high-pitched sounds that are generally inaudible to the human ear. A Cochrane review including 10 studies concluded there was no evidence that these devices repel mosquitoes to any degree [53].
PERMETHRIN-TREATED CLOTHING —
Permethrin is a synthetic compound applied to clothing or bedding (but not to skin) for the prevention of insect bites. Permethrin is active against mosquitoes, flies, ticks, and chiggers.
●Mechanism – Permethrin is an insecticide and an acaricide. It causes nervous system toxicity to insects; insects encountering permethrin-treated material become unable to move normally if they remain in contact for even a short amount of time [54].
Permethrin resistance is increasing among several mosquito species worldwide [55], although resistant arthropods may still be repelled by the compound [56]. (See "Malaria: Epidemiology, prevention, and elimination", section on 'Insecticide-treated nets (ITNs)'.)
●Use – Permethrin is available as a spray for the treatment of clothing and gear. Factory-permethrin-impregnated clothing is also available.
Fabrics should be sprayed on both sides for 30 to 45 seconds and allowed to dry completely before wearing. One application maintains potency for at least two weeks, even after several washings [57,58].
Several studies have indicated a substantial loss of permethrin after clothing is worn and laundered over an extended time, reducing protection to suboptimal levels [59-62]. Retreatment or replacement, semi-annually or annually, may be needed.
●Efficacy
•Mosquitoes – In a study of permethrin-treated military uniforms, protection from mosquito bites results with mosquito species, ranging from 68 percent bite reduction after 30 washes to 100 percent protection after 50 washes [63].
•Ticks – In a randomized trial, subjects wearing treated permethrin-treated clothing were 3.36 times less likely to have nymphal Ixodes scapularis ticks attach to their skin than subjects wearing untreated clothing. In addition, ticks that did attach to subjects with treated clothing were more likely to be dead within 2.5 hours of attachment [64].
Permethrin-treated clothing should be used in conjunction with topical repellants for optimal tick protection; this is because ticks commonly gain access to areas of skin where topical repellents are not applied.
●Adverse effects – Toxicity in humans is low [11]. Products made with permethrin carry no warnings about use in children or pregnant women.
INFORMATION FOR PATIENTS —
UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Insect bites and stings (The Basics)")
●Beyond the Basics topic (see "Patient education: Bee and insect stings (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Prevention goals – Goals for prevention of arthropod bites include reducing the risk of arthropod-borne infections (such as malaria, dengue fever, Zika virus infection, yellow fever, and others) and avoiding the nuisance of biting arthropods (such as itching and local bite reactions). (See 'Prevention goals' above.)
●Mosquito bites (see 'Preventing mosquito bites' above)
•Regions with high risk of mosquito-borne disease transmission (such as in malaria-endemic areas) – The most effective approach to preventing mosquito bites in these regions includes application of topical repellent to exposed skin, combined with use of permethrin-treated clothing.
For choice of topical repellent, we favor N,N-diethyl-3-methylbenzamide (DEET; 10 to 35 percent), given its favorable efficacy and durability. Microencapsulated formulations provide longer duration of protection with lower repellant concentrations.
Picaridin (up to 30 percent) is reasonable for individuals who wish to avoid the unpleasant characteristics of DEET (which may include skin irritation, damage to some materials) and are willing to accept a potentially less effective or shorter-acting repellent.
•Regions with low risk of mosquito-borne disease transmission – For individuals who wish to avoid nuisance mosquito bites in these regions, reasonable approaches include applying topical repellent (DEET or picaridin), with optional use of permethrin-treated clothing.
Less studied repellents include oil of lemon eucalyptus (PMD), ethyl butylacetylaminopropionate (IR3535), and BioUD (2-undecanone). Available data suggest these are less effective than DEET or picaridin.
•Behavioral interventions – Interventions to reduce the risk of mosquito bites include modifying activities to avoid mosquito bites, eliminating standing water, and maintaining screens on windows and doors.
●Tick bites (see 'Preventing tick bites' above)
•Prevention – The most effective approach to tick bite prevention includes application of topical repellent (DEET or picaridin) to exposed skin, combined with use of permethrin-treated clothing. Use of permethrin-treated clothing is important because ticks commonly gain access to areas of skin where topical repellents are not applied.
•Behavioral interventions – Interventions to reduce the risk of tick bites include dressing to minimize tick access to skin and visual inspection of the skin after time spent outdoors.
●Application technique – Insect repellents should be applied to maximize effectiveness and minimize adverse effects, as described above. (See 'Application technique' above.)
