Skin repellents are effective. The problem is that they are sold as complete protection when they are only a supplement, and that protection ends when you forget to reapply. Here is why a physical barrier belongs at the bed, the window and the door.
DEET works. Picaridin works. Both are effective repellents, and both have a real, legitimate role in protection.
The best comparative data still comes from Fradin and Day, who tested sixteen products on fifteen volunteers. They published the results in the New England Journal of Medicine in 2002. A formulation containing 23.8 percent DEET kept mosquitoes off the skin for an average of 301.5 minutes, just over five hours, the longest of any product tested. All the other botanical repellents protected for less than twenty minutes on average, and the repellent-impregnated wristbands offered no protection at all. The study measured the time to the first bite on a forearm held in a cage of mosquitoes, a strict test of how long a product really holds. The gap between those results is what the label never shows.
Picaridin belongs in the same effective group. It is registered by the United States Environmental Protection Agency and recommended by the Centers for Disease Control and Prevention. The CDC lists it among the repellents proven safe and effective when used as directed. The CDC names DEET, picaridin, IR3535, oil of lemon eucalyptus and 2-undecanone as the active ingredients in the repellents it recommends. Repellents are effective tools, and they have a real, legitimate role.
So what is the problem?
The problem is not the chemistry. It is the story that gets told around it.
Look closely at that five-hour figure. It is the ceiling, measured on a still forearm in a cage, and it is a countdown. Fradin and Day also found that a spray with only 4.75 percent DEET lasted 88 minutes, and that lower-concentration products can fade in an hour or two. Protection does not simply stop being reliable at some published hour. It stops the moment the film on your skin thins out, and it stops completely the moment you forget to reapply. The active ingredient does exactly what the label promises. The weakness is in the routine. You are hot, you are busy, the evening runs long, and the reapplication that the label quietly depends on never happens. That is not a laboratory failure. It is the ordinary way a real evening goes.
Then there is what the repellent leaves behind. A skin repellent is, by design, a chemical film you wear. It sits on your arms and legs, it transfers to clothing and bedding, and it is reapplied through the day. Used as directed, EPA-registered repellents are considered safe, including for pregnant and breastfeeding women. That is worth saying plainly. But "safe when used as directed" is not the same as "nothing to think about". Direct, repeated skin contact and residue are a genuine trade-off. A household that reaches for the spray a dozen times a day carries more of that trade-off than the label conversation usually admits. A similar trade-off applies elsewhere: burning a single mosquito coil indoors can release fine particulate matter equivalent to dozens of cigarettes. What you put on your skin, and what you burn in the room, is never simply free.
Effective, but not a barrier
A repellent is a supplement, not a barrier, and not a system.
It is sold, too often, as complete protection: one bottle, problem solved. It is not. A repellent does not cover the baby asleep in the next room. It does not protect an open window while the family watches television. It does not work while you sleep unless you are willing to coat your skin and reapply through the night, which almost nobody does and no one should have to. A spray protects the person wearing it, for as long as the film lasts, as long as they remember. That is a supplement to protection, not the whole of it.
The mode of action that medicine keeps returning to is the physical barrier: a mesh between human and mosquito. It has nothing to inhale and no residue on the skin. A correctly rated net protects a bed, a balcony or a garden enclosure for years, not hours, and it does not depend on anyone remembering anything. It works while you sleep. A well made, intact, correctly used barrier is real protection whether or not it carries an active ingredient. The failure to avoid is the wrong mesh, poor durability and no certification, not the absence of chemistry.
None of this is a reason to panic. Vector-borne diseases still cause well over seven hundred thousand deaths a year, the great majority through malaria, with dengue also fatal. Chikungunya, by contrast, is often disabling but rarely fatal (WHO). Those stakes are why honesty about protection matters more than a scary sentence. The goal is to help you reduce your risk, not to frighten you into a purchase.
So keep the DEET or the picaridin. They earn their place in a rucksack, on a trail, on a summer evening in the garden. Use the concentration that suits the exposure, follow the label, and reapply. Just do not mistake the bottle for the whole of your protection. Put the barrier first, at the bed and the window and the door, and let the repellent cover the stretch when no barrier can.
Sources: Fradin and Day, comparative efficacy of insect repellents, NEJM 2002 | CDC, prevent mosquito bites (repellent safety and recommended active ingredients) | WHO, vector-borne diseases fact sheet | Liu et al., mosquito coil emissions and health implications, EHP 2003 | WHO, chikungunya fact sheet
Medical disclaimer: this article is general information, not medical advice. For guidance on disease risk, pregnancy, infants, or specific health conditions, consult a qualified healthcare professional.
This article is general information, not medical advice. Ask a doctor or pharmacist about your own health.