Raid kills cockroaches by attacking their nervous system. The active ingredients in most Raid sprays are synthetic pyrethroids, chemicals that force open the nerve cells’ sodium channels so they can never close again. This causes uncontrollable nerve firing, paralysis, and death, often within minutes of contact.
How Pyrethroids Shut Down the Nervous System
Insect nerve cells communicate through tiny gates called sodium channels. When a signal travels down a nerve, these channels open briefly to let sodium ions rush in, then snap shut so the nerve can reset for the next signal. Pyrethroids like imiprothrin and cypermethrin, two of the most common active ingredients in Raid products, jam those channels in the open position. Sodium keeps flooding in, and the nerve fires over and over with no way to stop.
The result is immediate and visible. You’ll often see a cockroach flip onto its back and twitch after being sprayed. That’s the nervous system short-circuiting. The insect loses the ability to coordinate its legs, breathe properly, or move. Paralysis sets in first, and death follows as the entire nervous system collapses.
Raid formulas typically pair a fast-acting pyrethroid with a longer-lasting one. The fast-acting ingredient delivers the “knockdown,” dropping the roach within seconds. The slower ingredient finishes the job and provides lasting protection on surfaces. Raid Ant & Roach Killer 26, for example, claims residual killing action for up to 13 weeks on non-porous surfaces like ceramic and laminate.
Bait Products Work Differently
Raid also makes bait stations and gel baits that use a completely different strategy. Instead of contact-killing with pyrethroids, these products contain slow-acting poisons that the cockroach carries back to its nest. The roach eats the bait, returns to its hiding spot, and dies. Other roaches then feed on the dead roach’s body or droppings, spreading the poison through the colony. This chain reaction can eliminate roaches you never see or spray directly.
Some Raid bait products also include ingredients that interfere with reproduction. Raid Plus Egg Stoppers, for instance, sterilizes cockroaches that come into contact with the bait, even if they don’t eat it. This breaks the breeding cycle so new generations never hatch, which matters because a single German cockroach egg case can produce 30 to 40 nymphs.
Why Raid Sometimes Doesn’t Work
If you’ve sprayed Raid directly on a cockroach and watched it run away apparently unharmed, you’re not imagining things. Cockroach resistance to pyrethroids is now widespread, particularly among German cockroaches, the small brown species most common in apartments and kitchens.
Research from North Carolina State University tested German cockroaches collected from apartments where foggers (bug bombs) had failed. The results were striking: apartment-collected roaches were roughly 200 times more resistant to cypermethrin than laboratory cockroaches that had never been exposed to insecticides. Over 96% of the tested cockroaches carried at least one copy of a genetic mutation that makes their sodium channels less sensitive to pyrethroids. Seventy-seven percent carried two copies, making them highly resistant. Only 4% had the normal, susceptible version of the gene.
These roaches have also developed a second defense: enzymes that break down the insecticide before it reaches the nervous system. Even when researchers added a chemical to block those enzymes, the cockroaches still survived unless hit with very high doses. In practical terms, this means a quick spray from a can may not deliver enough active ingredient to kill a resistant roach, especially if it only gets a glancing dose.
This is one reason pest control professionals often recommend bait-based approaches over sprays for serious infestations. Baits use different chemical classes that cockroaches haven’t developed the same level of resistance to, and they reach roaches hiding deep inside walls and appliances that a spray never touches.
How Residual Protection Works on Surfaces
When you spray Raid on a baseboard or under a sink, a thin film of active ingredient dries onto the surface. Any cockroach that walks across that film picks up the chemical on its legs and body. The pyrethroid absorbs through the insect’s exoskeleton and reaches the nervous system, triggering the same sodium channel disruption as a direct spray.
This residual layer is what Raid means when it advertises “keeps killing” after the initial application. The 13-week figure applies specifically to hard, non-porous surfaces. On porous materials like wood or fabric, the chemical absorbs into the material and breaks down faster, reducing its effectiveness. Cleaning the sprayed surface also removes the residue.
Safety Around People and Pets
Pyrethroids are far more toxic to insects than to mammals because insects have more sensitive sodium channels and much smaller bodies. That said, the chemicals aren’t harmless. Pets are more vulnerable than humans, especially cats, which lack certain liver enzymes needed to break down pyrethroids efficiently.
The National Pesticide Information Center recommends removing pets, their food bowls, water dishes, bedding, and toys from any area before spraying. Keep animals out of the treated space until the spray has dried completely, or longer if the product label specifies a re-entry time. Good ventilation during drying helps the solvent evaporate faster and reduces the amount of chemical lingering in the air.
Fish are particularly sensitive. If you use any aerosol insecticide, cover fish tanks and turn off the air pump so the spray mist doesn’t get pulled into the water. Turning off central heating or air conditioning prevents the HVAC system from circulating airborne particles to other rooms where pets or children may be present.