Ants are not dangerous creatures, and if they enter your home, they do not pose any health risks to you, your children, or your pets. If they get into your food, you may no longer wish to eat that food, but if you accidentally consume a few ants, nothing will happen to you. High school biology teachers have been known to feed chocolate-covered ants to their students; this has never resulted in an illness or a lawsuit.
Ants are simply a nuisance; most people would prefer not to have heavily trafficked ant highways crisscrossing their kitchen countertops. Exterminators can spray chemicals in your house that will eradicate your ants, but this solution makes no sense. Why would you flood your kitchen with chemicals that are toxic, in order to clear out small insects that are not toxic in the least? There are plenty of safe, nontoxic solutions to an ant invasion.
You may be tempted to wipe away the ants that are visible on your countertop with a sponge, killing these exposed ants but leaving at least a few carcasses on the floor or in cracks where you can't see them. This practice will only encourage more ants to swarm to the scene; ants are attracted by the odor given off by their dead companions, and they will begin arriving en masse to carry off the dead. It is best to focus on keeping the ants out of your house to begin with.
Try to find out where they're coming in. If they regularly appear on your kitchen countertop, check around nearby windows for cracks or openings. If your countertop is held together in places with silicone rubber or caulk, make sure there are no gaps. Check inside all your cabinets for gaps in the woodwork, and wipe away any spilled food while you're at it. And keep your kitchen clean, particularly around windowsills. Ants have a talent for quickly locating even just a few scattered grains of sugar, an invisible smudge of banana.
There are many common household substances that are repellent to ants. If an ant encounters cinnamon, mint, red chili powder, or black pepper, he will crawl quickly in the other direction. You can sprinkle any of these spices lightly around your countertops or inside your cupboards. Bay leaves dipped in mint mouthwash will also drive away ants; you can place several bay leaves around windowsills. If you want a solution that is less messy, you can plant mint and cloves in small pots and keep these around your kitchen windowsills, or outdoors in small gardens just outside your house walls.
Ants will not cross any lines drawn with chalk or Vaseline; you can try drawing chalk lines along your windowsills or along seams in your cabinetry. Ordinary chalk made of gypsum may not work; tailor's chalk, made of talc, is effective. The active ingredient here is the talc; baby powder is another harmless household substance containing talc that ants try to avoid.
A solution of equal parts vinegar and water, sprinkled around your counters and food preparation areas, will keep ants away, though with vinegar you may just be swapping one annoyance for another. A glass cleaner such as Windex will also prevent ants from coming, but as with the vinegar, this solution may be a bit invasive.
Some species of ants indeed can be damaging. Carpenter ants, for instance, can hollow out woodwork in your house; they don't eat the wood, but build their nests in hollowed-out areas. Termites do indeed eat wood, and can cause extensive damage to your home. Either of these pests should be cleared out as quickly as possible, using whatever means you have available. And fire ants (or "red ants") will sting. There are 280 species of fire ants worldwide, with some species occurring in Australia and the southern and southwestern United States. But, in almost all cases, the ants you find in your house will be harmless, and you can experiment with different safe, nontoxic ways of getting rid of them.