Bug spray can make you sick, though the risk depends heavily on the product, how you use it, and how much gets into your body. The most widely used repellent ingredient, DEET, has a strong safety record when applied as directed, but it does cross the skin barrier and enter the bloodstream, and misuse or heavy exposure can cause symptoms ranging from skin irritation and headaches to, in rare cases, seizures. The story gets more interesting when you look at what else is in the can, who is spraying it, and what other products are on your skin at the same time.
What Happens When DEET Gets Through Your Skin
DEET (N,N-diethyl-meta-toluamide) has been used as an insect repellent since the 1950s, and the reason it occasionally causes problems is straightforward: it absorbs through the skin and enters the bloodstream. Research has shown that adverse effects from DEET-containing products appear to result from this significant skin absorption, and that the formulation itself matters a great deal. Products that use ethanol as a solvent can dramatically increase how much DEET passes through your skin. One study found that certain ethanol concentrations boosted DEET’s skin permeation rate by over 150% compared to DEET applied alone.1International Journal of Pharmaceutics. Formulation of topical insect repellent N,N-diethyl-m-toluamide (DEET): vehicle effects on DEET in vitro skin permeation That means the bug spray you grab off the shelf isn’t just delivering DEET to your skin; the alcohol base is actively helping it get deeper.
Alternative formulations can reduce this permeation, and some researchers have argued that current commercial products haven’t been optimized for safety in this respect.2PubMed. Reduction in skin permeation of N,N-diethyl-m-toluamide (DEET) by altering the skin/vehicle partition coefficient For now, the practical takeaway is that slathering on more product or reapplying frequently increases how much DEET enters your body, and that sprays with high alcohol content tend to push more of it through.
Common Symptoms From Repellent Exposure
Most people who feel unwell after using bug spray experience relatively mild symptoms. The typical complaints include skin redness, rash, or a burning or tingling sensation at the application site. Eye irritation is common when spray drifts during application. Nausea, headache, and dizziness can occur when a person inhales aerosolized repellent in a poorly ventilated area or applies excessive amounts to exposed skin. For people with sensitive skin or a history of eczema, even one application can trigger a flare-up.
More serious reactions, though uncommon, have been documented in case reports over DEET’s decades-long history. These include tremors, confusion, and seizures, almost always linked to ingestion, application to broken skin, or extreme overuse. A comprehensive review of DEET’s safety literature concluded that its continued use is endorsed by both the CDC and EPA, with the caveat that specific guidelines exist for how it should be applied to children.3PubMed. Is DEET a dangerous neurotoxicant? The pattern in serious cases is almost always the same: too much product, applied too often, or used in ways the label never intended.
How DEET Affects the Nervous System
One of the more debated questions in repellent toxicology is whether DEET acts on the human nervous system. The answer is nuanced. DEET does inhibit an enzyme called acetylcholinesterase, which is critical for nerve signaling, but research shows it does so only weakly. Lab studies found that DEET required very high concentrations (in the millimolar range) to meaningfully block this enzyme in both insect and human nerve preparations.4PubMed Central. Neurotoxicity and mode of action of N, N-diethyl-meta-toluamide (DEET) At the concentrations a person would realistically absorb through their skin, this effect is considered minimal.
That said, the story isn’t entirely reassuring. Separate research confirmed that DEET does inhibit cholinesterase activity in mammalian nerve tissue and, more concerning, that it can strengthen the toxicity of carbamate insecticides, a class of chemicals that works by blocking the same enzyme.5PubMed Central. Evidence for inhibition of cholinesterases in insect and mammalian nervous systems by the insect repellent deet This matters because people who work in agriculture or pest control may be exposed to both DEET and carbamate-based insecticides at the same time. For the average person spraying on repellent before a hike, the neurological risk from DEET alone is low. For someone handling multiple pesticide products daily, the combined exposure warrants more caution.
Inhaling Bug Spray Is a Different Problem
Spray cans create a fine mist, and some of it inevitably ends up in your lungs. For most healthy people, a brief whiff causes nothing worse than a cough or mild throat irritation. But for people with asthma, the effects can be clinically meaningful. A controlled study exposing asthmatic subjects to standard insecticide aerosols found that lung function dropped measurably after exposure, with one aerosol causing a statistically significant fall in the volume of air people could force out in one second. Beyond that acute dip, the aerosols also increased airway hyperresponsiveness, meaning the lungs became more reactive to triggers for a period after the exposure.6PubMed. The effect of insecticide aerosols on lung function, airway responsiveness and symptoms in asthmatic subjects
The practical lesson here is to apply spray-on repellents outdoors or in well-ventilated spaces, never directly at the face, and to opt for lotions or wipes if you have asthma or other lung conditions. If you’re spraying it onto your face area (which most labels advise against), spray it onto your hands first and then rub it on.
The Sunscreen Combination Problem
Many people apply both sunscreen and bug spray during outdoor activities, and there’s good evidence that this combination changes how much of each chemical gets into your body. Multiple studies have shown that DEET and oxybenzone (a common sunscreen ingredient) enhance each other’s skin penetration when applied together. One research group found that combined application boosted percutaneous penetration by anywhere from 36% to 108%, depending on the formulation.7PubMed. Percutaneous characterization of the insect repellent DEET and the sunscreen oxybenzone from topical skin application An in vitro study using pig skin showed even higher enhancement for certain solvents, with DEET permeation jumping nearly threefold in some formulations when oxybenzone was present.8Journal of Pharmacy and Pharmacology. In-vitro permeation of the Insect repellent N,N-diethyl-m-toluamide (DEET) and the sunscreen oxybenzone
A human study confirmed this isn’t just a lab curiosity. Applying oxybenzone-containing sunscreen over DEET on the skin led to significantly higher DEET absorption, as measured by urinary metabolites. The researchers recommended that if you need both products, you should apply sunscreen first, wait about 15 minutes, and then apply the DEET-based repellent on top.9PubMed. Assessment of dermal absorption of DEET-containing insect repellent and oxybenzone-containing sunscreen using human urinary metabolites Combination products that mix sunscreen and repellent in one bottle are generally considered a worse option because they force you to reapply both at the sunscreen’s shorter reapplication interval, increasing your cumulative DEET dose.
Picaridin as a Lower-Risk Alternative
If DEET’s absorption profile concerns you, picaridin (also sold as icaridin) is worth knowing about. This repellent works against the same range of insects, and its safety profile is notably cleaner. A review of poison control data covering tens of thousands of insect repellent exposures found that among picaridin-containing products, nearly 93% of cases were managed outside of a healthcare facility. There were no reported deaths, no major effects, and only a single case of moderate effect.10PubMed. The toxicity of picaridin containing insect repellent reported to the National Poison Data System
Part of the reason for this safety gap is that picaridin doesn’t cross the skin as readily. Comparative permeation studies found that picaridin’s transdermal absorption through human skin was significantly lower than DEET’s, both when used alone and when combined with oxybenzone sunscreen. Unlike DEET, picaridin didn’t show a synergistic permeation boost when paired with oxybenzone; if anything, their concurrent use either suppressed or didn’t change picaridin’s absorption.11Die Pharmazie. Percutaneous permeation comparison of repellents picaridin and DEET in concurrent use with sunscreen oxybenzone from commercially available preparations For people who need both sun and bug protection, picaridin sidesteps one of DEET’s most practical drawbacks.
Permethrin on Clothing Is Mostly Safe, With Caveats
Permethrin-treated clothing is popular for tick and mosquito protection, especially among hikers and military personnel. It works differently from skin-applied repellents: permethrin kills insects on contact and is meant to stay on fabric, not skin. Still, some transfer happens. A study measuring permethrin migration from treated military uniforms found that over a week of wear, about 3% of the available permethrin reached the skin, with most of that amount actually being absorbed into the body. The predicted daily exposure dose for a person wearing treated clothing was extremely low.12PubMed. Permethrin transfer from treated cloth to the skin surface: potential for exposure in humans
A more detailed study tracking permethrin metabolites in volunteers who wore treated clothing for a single eight-hour period found measurable internal exposure, with concentrations peaking during or shortly after wear and then declining with a half-life of roughly 38 hours. The amount absorbed increased with higher temperature, humidity, and physical exertion, all of which compromise the skin’s barrier function.13PubMed. Uptake and elimination of permethrin related to the use of permethrin treated clothing for forestry workers For occasional recreational use, permethrin-treated clothing appears to pose minimal risk. For forestry workers or military personnel wearing it daily in hot conditions for weeks, the cumulative exposure is worth monitoring.
Children Absorb More Per Pound
Kids face a higher risk from topical chemicals than adults for a simple anatomical reason: they have a much larger skin surface area relative to their body weight. This means that the same amount of product applied to a child’s skin results in a proportionally bigger dose entering their bloodstream. Infants and very young children are especially vulnerable because their skin barrier is also less mature, allowing chemicals to pass through more readily.14Pediatric Clinics of North America. TOPICAL THERAPIES AND MEDICATIONS IN THE PEDIATRIC PATIENT
The CDC recommends against using DEET-based products on infants under two months of age. For older children, the standard advice is to apply the product to your own hands first and then rub it onto the child, avoiding hands, eyes, and mouth. Products with DEET concentrations above 30% are unnecessary for children since higher concentrations extend duration of protection but don’t improve repellency, and they increase the total amount absorbed. Oil of lemon eucalyptus products should not be used on children under three.
Pregnancy and DEET
Pregnant women in mosquito-heavy regions face a genuine dilemma: malaria and other mosquito-borne diseases pose serious risks to the fetus, but so does any chemical crossing the placenta. The best available evidence is reassuring. A study following pregnant women who used DEET regularly during their second and third trimesters found that DEET did cross the placenta and was detectable in about 8% of cord blood samples from a randomly selected subgroup. Despite this, there were no adverse effects on survival, growth, or development at birth or at the one-year follow-up.15American Journal of Tropical Medicine and Hygiene. Safety of the insect repellent N,N-diethyl-M-toluamide (DEET) in pregnancy
An early animal study had raised alarm by reporting embryotoxicity from DEET, but other investigators were unable to replicate the finding.16PubMed. Review of the biodistribution and toxicity of the insect repellent N,N-diethyl-m-toluamide (DEET) The current consensus, endorsed by both the CDC and EPA, is that DEET is safe for use during pregnancy when applied properly.3PubMed. Is DEET a dangerous neurotoxicant? The theoretical risks of wearing repellent should be weighed against the very real dangers of diseases like malaria, dengue, and Zika, which can have devastating effects on fetal development.17PubMed Central. Assessment of methods used to determine the safety of the topical insect repellent N,N-diethyl-m-toluamide (DEET)
“Natural” Repellents Aren’t Automatically Safer
There’s a widespread assumption that plant-based bug sprays are gentler than synthetic ones. This isn’t consistently true. Essential oils used in natural repellent products, including citronella, lemongrass, and eucalyptus oils, are increasingly associated with allergic contact dermatitis, a delayed skin reaction that can cause itching, redness, blistering, and swelling. As the popularity of essential oil products has grown, so have reports of these reactions.18PubMed Central. Art of Prevention: Essential Oils – Natural Products Not Necessarily Safe
Beyond skin reactions, many natural repellents wear off much faster than DEET or picaridin, requiring more frequent reapplication and potentially more total skin exposure. And because the EPA regulates essential oil repellents less strictly than synthetic ones (many qualify for an exemption from registration), there’s less standardized safety testing behind them. A product labeled “natural” may contain allergenic compounds at concentrations that would receive more scrutiny if the active ingredient were synthetic.
The Ingredients You Don’t See on the Label
Most of the attention around bug spray safety focuses on the active ingredient, but commercial formulations contain a cocktail of other chemicals: solvents, propellants, fragrances, and surfactants. These so-called “inert” ingredients are often less well-studied and, in some cases, more toxic than the active principle itself. Research has shown that in the broader pesticide industry, commercial product formulations are frequently more toxic than the active ingredient alone, with the added adjuvants accounting for the increased harm.19Frontiers in Public Health. Ignoring Adjuvant Toxicity Falsifies the Safety Profile of Commercial Pesticides A systematic review found that in 24 separate studies, the full commercial product was more toxic than its active ingredient in isolation, and this difference was attributed to the adjuvants in the formulation.20PubMed. Systematic review of comparative studies assessing the toxicity of pesticide active ingredients and their product formulations
For consumers, this means that switching between two products with the same active ingredient and concentration isn’t necessarily a neutral swap. The solvent base, the propellant, and other unlisted additives can change the product’s skin penetration, its tendency to irritate mucous membranes, and its overall toxicity profile. If you react to one DEET product but not another, the inactive ingredients are the likely culprit.
Permethrin and Cats
If you have cats, permethrin deserves a separate warning. Dogs tolerate permethrin well enough that it’s a common ingredient in canine flea treatments, but cats are exquisitely sensitive to it. A review of 286 cases of cats accidentally exposed to permethrin-based spot-on products found that almost 97% developed symptoms. Muscle twitching, tremors, and convulsions appeared in roughly 88% of affected cats, and the episodes were prolonged, with convulsions lasting an average of about 39 hours. Death occurred in about one in ten cases.21PubMed Central. Clinical effects and outcome of feline permethrin spot-on poisonings reported to the Veterinary Poisons Information Service (VPIS), London
The explanation involves more than just metabolism. Cats are small, they groom obsessively (turning a skin exposure into an oral one), and they lack efficient pathways for clearing pyrethroids from their bodies. High-concentration dog products applied to a cat, or transferred through physical contact between a freshly treated dog and a cat in the same household, are the most common scenarios.22PubMed. Permethrin in companion animals: Mechanistic neurotoxicity, dermal pharmacokinetics, and secondary exposure pathways If you treat your dog with a permethrin-based product and share your home with a cat, keep them separated until the product has fully dried, and be aware that residue on bedding or furniture can still be transferred.
What to Do if You or Someone Else Has a Reaction
If bug spray gets on your skin and you notice irritation, wash the area with soap and water as quickly as possible. Delay matters: research on skin decontamination has shown that longer exposure times before washing are associated with reduced effectiveness of the cleanup, meaning more of the chemical has already been absorbed.23Nature. Management of decontamination in chemical accidents: a laboratory model For eye exposure, flush with clean water for at least 15 minutes. If someone has swallowed bug spray, call poison control (1-800-222-1222 in the United States) rather than inducing vomiting, since some formulations can cause additional damage coming back up.
Symptoms that should prompt a trip to the emergency room include seizures, difficulty breathing, persistent vomiting, or altered mental status. These are rare with repellent-grade products used on skin, but they can occur with ingestion or extreme overexposure. Bring the product container with you so medical staff can identify the active and inactive ingredients quickly.
Reducing Your Risk Without Giving Up Protection
The mosquito-borne diseases that repellents prevent remain far more dangerous than the repellents themselves. In regions where malaria, dengue, Zika, or West Nile virus circulate, going without protection carries serious risk. A reasonable approach to minimizing repellent exposure while staying protected includes a few simple habits:
- Use the lowest effective concentration. For DEET, 20-30% is sufficient for most outdoor activity lasting several hours. Higher concentrations last longer but don’t repel more effectively, and they increase absorption.
- Apply to clothing when possible. Spraying sleeves and pant legs rather than bare skin reduces how much enters your body.
- Wash it off when you come inside. There’s no benefit to leaving repellent on your skin after the mosquitoes are no longer a threat.
- Separate sunscreen and repellent. Apply sunscreen first, let it absorb for 15 minutes, then apply repellent on top. Avoid combination products.
- Consider picaridin. If you’re concerned about skin absorption or regularly use sunscreen, picaridin absorbs less through the skin and doesn’t interact synergistically with oxybenzone.
Repellents are one of public health’s most effective frontline tools against vector-borne disease, and the evidence supports their continued use for the general population, including pregnant women and children over two months.17PubMed Central. Assessment of methods used to determine the safety of the topical insect repellent N,N-diethyl-m-toluamide (DEET) Most of the genuine risks come down to misuse, overuse, or failing to account for interactions with other products on your skin.