Keeping ants out of your house comes down to three things: removing what attracts them, sealing how they get in, and eliminating the colony if they’ve already established trails. Most ant problems can be solved without professional help if you address all three at once, but knowing which type of ant you’re dealing with makes your efforts far more effective.
Identify What You’re Dealing With
Not all ants respond to the same strategies. The most common indoor species behave differently and nest in different places, so a quick identification saves you time and money.
Odorous house ants are the most frequent invaders in many regions. They’re medium-sized, nest outdoors under mulch and stones, and are drawn to sweets. Crush one and you’ll notice a distinctive licorice-like smell. They’ll also nest inside wall voids and bricks, especially near moisture.
Carpenter ants are larger (1/4 to 1/2 inch), often black or a mix of black and red-orange, and mostly active at night. They don’t eat wood, but they hollow it out to build nests, which means they can cause real structural damage over time. A telltale sign is small piles of sawdust-like debris (called frass) near wooden structures.
Pharaoh ants are tiny, yellowish, and almost exclusively indoor nesters. They set up colonies in dark, narrow spaces like electrical boxes, wall voids, and cardboard boxes. They’re picky eaters that alternate between sugary and protein-rich foods, and they typically require specially formulated baits rather than general-purpose products.
Cut Off Food and Moisture
Ants forage indoors for two things: food and water. In nature, many ant species feed on nectar and the sugary secretions of aphids. Inside your home, they’ll settle for anything from the trash can to the cereal bowl to a sticky spot on the counter.
Start with the obvious: wipe down counters and stovetops daily, sweep floors where crumbs accumulate, and store sugar, honey, and syrup in sealed containers. Don’t leave pet food dishes out overnight. Take trash out regularly, and use bins with tight-fitting lids. Even a thin film of juice residue on a recycling bin is enough to sustain a foraging trail.
Moisture matters just as much as food. Ants nest near water sources, and colonies have been found inside appliances, potted plants, and wall cavities near leaky pipes. Fix dripping faucets, dry out under-sink areas, and check for condensation around air conditioning units. If you have a bathroom where the grout stays damp or a basement with standing humidity, a dehumidifier makes the space far less hospitable.
Seal Entry Points
Ants can squeeze through gaps as small as 1/16 of an inch, so sealing your home is one of the most effective long-term strategies. Start by lying on the floor near each exterior door and checking for light filtering underneath. If you can see light, ants can get through. Install door sweeps or thresholds, and apply caulk along the bottom outside edge and sides of door thresholds.
Other common entry points include:
- Utility openings: gaps where pipes and wires enter the foundation, around outdoor faucets, gas meters, dryer vents, and cable TV wires
- Windows and fascia boards: cracks along frames and trim
- Sliding glass doors: gaps along the bottom track
- Garage doors: the seal along the bottom edge
For most cracks around windows and doors, a good quality silicone or acrylic latex caulk works well. Latex caulks clean up easily with water and can be painted over. Clear-drying caulk is more forgiving than pigmented versions if your lines aren’t perfect. For larger holes around utility penetrations, expandable foam, steel wool, or copper mesh all work. Line sliding door tracks with 1/2 to 3/4 inch foam weatherstripping. Garage doors do best with a rubber bottom seal, since vinyl tends to crack in cold weather.
Use Baits to Eliminate the Colony
Killing the ants you can see is the least effective approach. Spraying a trail with contact killer removes the foragers but leaves the colony intact, and new workers simply find a different path. Baits work differently, and far better, because foraging ants carry the bait back to the nest and share it with the queen and larvae through a process called trophallaxis (essentially mouth-to-mouth feeding).
Effective ant baits use slow-acting ingredients at very low concentrations. Common active ingredients include boric acid, sodium borate, and fipronil. The toxicity is low enough that ants make no connection between the bait and the deaths occurring in the colony, so they keep feeding at the stations for weeks while toxin levels gradually build. This slow accumulation is what eventually collapses the colony from the inside.
Place bait where you see ants actively foraging, then watch for a few minutes to confirm they’re feeding on it. Good spots include behind appliances, under sinks, along baseboards, and near cabinets. Keep bait out of reach of children and pets, and never place it directly on food-preparation surfaces or where it could contaminate water sources. For large colonies, you may need bait in multiple locations.
Expect to keep seeing ants for a week or more after baiting. That’s a sign the system is working, because those foragers are still carrying poison back to the nest. Leave the bait in place for three to four days after you see no more signs of ant activity.
One important note: if you’re dealing with ants attracted to sweets, use a sugary gel or liquid bait. If they’re ignoring sweet bait, switch to a protein-based option. Some species, like pharaoh ants, alternate between the two, so you may need both types available.
Outdoor Perimeter Control
Since most ant colonies nest outdoors and send foragers inside, treating the perimeter of your home creates a barrier between the colony and your living space. You can apply granular or liquid insecticide to a band of soil and vegetation up to seven feet wide around your foundation, and treat the foundation wall itself up to about two feet high.
Apply perimeter treatments only to porous surfaces like soil, mulch, and lawn. Avoid spraying onto driveways, sidewalks, or any surface that drains into storm sewers. Treat under eaves, soffits, and around exterior entry points like doorways and windows as well. These treatments typically need reapplication every few months, especially after heavy rain.
For a less chemical approach, keep mulch, leaf litter, and ground cover pulled back from your foundation by at least a few inches. Trim tree branches and shrubs that touch your house, since carpenter ants in particular follow branches, fences, and even garden hoses as highways into buildings.
Natural Deterrents and Their Limits
Food-grade diatomaceous earth works by physically damaging the waxy coating on an ant’s exoskeleton, causing dehydration. Dust it lightly into cracks, along baseboards, and in other dry areas where ants travel. The key limitation is that it must stay dry to be effective. In humid areas, under sinks, or outdoors after rain, it loses its potency entirely.
Essential oils like peppermint and tea tree oil act as short-term repellents. A spray of 10 to 20 drops diluted in a bottle of water can discourage ants from a specific area temporarily. They won’t eliminate a colony, but they can be useful for redirecting ants away from a kitchen counter while your baits do the real work.
Neither of these approaches solves an established infestation on its own. They work best as supplements to sealing, sanitation, and baiting.
When the Problem Needs Professional Help
Most ant invasions respond well to the combination of sanitation, sealing, and baiting. But certain situations call for professional pest control. If you suspect carpenter ants, getting an expert involved quickly is worth it, because the structural damage they cause compounds over time. Signs include frass near wooden structures, small holes in wood, and crumbling woodwork in damp areas.
Other signals that it’s time to call a professional: you’ve tried DIY methods and ants keep returning (suggesting a larger colony or multiple colonies), you’re seeing ant trails in several different rooms simultaneously, or you’ve had repeated infestations within a short span. A pest control professional can identify species accurately, locate hidden nests, and apply targeted treatments that aren’t available over the counter.