The fastest way to kill ants inside your home is with bait stations, not sprays. Sprays only kill the ants you can see, while baits wipe out the entire colony, including the queen that keeps producing new workers. Getting rid of an indoor ant problem takes a combination of cleaning up their scent trails, placing the right bait, and sealing the gaps they’re using to get in.
Why Bait Works Better Than Spray
When ants find food, they carry it back to the nest and share it mouth-to-mouth with other ants, including the queen. This food-sharing behavior is the key to eliminating a colony. Slow-acting bait exploits it perfectly: foraging ants pick up the poisoned bait, carry it underground, and spread it through the entire colony during feeding. The queen dies, egg production stops, and the colony collapses.
Spraying ants with a contact killer does the opposite of what you want. It wipes out the visible foragers, but the queen and thousands of workers deeper in the nest are untouched. Within days, new foragers replace the dead ones. Worse, some ant species respond to spray by “budding,” where the colony splits into multiple smaller colonies that scatter to new locations in your walls. Pharaoh ants are especially notorious for this.
Bait takes patience. You won’t see results for at least a week, sometimes two. During that time, you’ll actually want to see ants visiting the bait, because that means they’re carrying poison home. Resist the urge to spray the trail while baiting. Let them do the work for you.
Choosing the Right Bait
Ants switch between craving sugars and craving proteins depending on the colony’s needs. If they ignore a sweet bait, try a protein or grease-based one. Many people set out both types side by side and let the ants choose. Gel baits work well along baseboards and in cracks. Pre-filled bait stations are convenient and keep the product away from kids and pets.
Borax mixed with sugar water is a popular DIY option. A common recipe is roughly one tablespoon of borax dissolved in half a cup of sugar water, soaked into cotton balls and placed along ant trails. Boric acid is low in toxicity for humans and pets at small doses, but it can cause poisoning in animals if eaten in large amounts, with symptoms starting within two hours. Keep homemade bait out of reach of dogs, cats, and children.
For the bait to reach the queen, it must be slow-acting. If ants die before making it back to the nest, the poison never spreads. This is why commercial ant baits use very low concentrations of active ingredients. Don’t add extra borax to a DIY mix thinking it will work faster.
Wipe Out the Scent Trails
Ants follow invisible chemical trails laid down by scouts. Even after you kill every ant you see, the next wave will follow the same path unless you destroy the trail. A 50/50 mix of white vinegar and water in a spray bottle does the job. Spray it directly along the ant trail, across entry points, windowsills, and doorways, then wipe the surface clean.
Adding a tablespoon of dish soap to the vinegar-water mix helps in two ways: the soap breaks the surface tension (which kills ants on contact) and helps the vinegar cling to surfaces longer. A few drops of peppermint oil in the mix adds a scent ants dislike, though it’s a deterrent rather than a killer. Clean the trail first, then place bait nearby so ants find your poison instead of their old food source.
Identify the Ant to Pick Your Strategy
Not all indoor ants are the same, and what works for one species can fail with another.
Odorous house ants are the most common invaders. They’re tiny, dark brown, and smell like rotten coconut when crushed. They nest in walls, under floors, and beneath objects on the ground outside. Standard sugar baits work well on them.
Pavement ants enter through cracks in concrete slabs and foundations. You’ll often see small mounds of dirt pushed up through floor cracks. They respond well to both sweet and protein baits.
Pharaoh ants are very small, yellowish, and nest exclusively indoors in northern climates. They build colonies in wall voids, behind baseboards, and near warm, moist areas. Never spray pharaoh ants. They bud aggressively, and a single colony can fracture into dozens. Bait is the only effective approach.
Carpenter ants are the largest common indoor ant, often black and about half an inch long. They don’t eat wood, but they excavate it to build nests, which means they can cause real structural damage over time. A telltale sign is small piles of sawdust-like shavings, sometimes mixed with insect parts, accumulating below a hole in wood or drywall. Their galleries are smooth and clean inside, unlike termite damage which is packed with mud. Carpenter ants are most active at night, so watching their movement after dark can help you locate the nest. They typically need professional treatment, especially if the nest is inside a wall void.
Seal the Entry Points
Killing the current colony is only half the job. If you don’t close off entry points, a new colony will find the same routes. Wait at least seven days after placing bait before sealing anything. If you seal too early, you risk trapping live ants inside your walls before the bait has done its work.
Focus on these areas first: the gap where your home’s wooden frame meets the concrete foundation, holes where pipes and cables enter the house, door thresholds, window frames (especially on sides that stay damp), and any spot where wood touches the ground outside.
For gaps under a quarter inch, 100% silicone caulk is the best option. It stays flexible through temperature changes and ants can’t chew through it. Use pure silicone, not the cheaper siliconized acrylic blends sold at hardware stores. For gaps between a quarter inch and one inch, fill with expanding foam labeled for pest control, then cap with a bead of silicone after the foam cures. For anything larger, pack copper mesh into the opening first, then foam over it and finish with silicone. Ants can chew through cured foam alone, but they won’t get through copper mesh. Skip steel wool for this purpose. It rusts within a season and leaves new gaps.
For doors, an automatic door sweep or an aluminum threshold with a vinyl seal insert closes the gap at the bottom where ants commonly enter.
Cut Off Their Food and Water
Ants are inside your home because they found food, water, or both. Reducing those resources makes bait more attractive (it becomes the best meal available) and makes your home less appealing to new colonies scouting the area.
Store sugar, honey, and pet food in sealed containers. Wipe counters and sweep floors daily during an active infestation. Don’t leave pet water bowls out overnight. Fix leaky faucets and pipes, especially under sinks, because moisture is a major draw for odorous house ants and carpenter ants alike. Take garbage out frequently and keep bins clean. Even a thin residue of soda or juice on a recycling bin is enough to sustain a trail of ants for weeks.
Rinse dishes immediately or load them into the dishwasher rather than stacking them in the sink. Move compost bins and fruit bowls away from exterior walls. If you have a pet, pick up food bowls between meals rather than leaving them accessible around the clock.