If you want to know what a home really looks like, ask a house cleaner. As professionals who tidy up and wipe off messes for a living, house cleaners know the truth of what’s really clean and sanitary in bedrooms and kitchens. And they’ve seen it all. “People don’t clean anything they or guests can’t readily see,” said Sara San Angelo, a house cleaner based in Charleston, South Carolina. House cleaners revealed to HuffPost the most common dirty appliances they see in homes. Let these be a lesson for us all, because some of these unclean areas are not just unsightly; they can be a safety hazard. The Microwave MediaProduction via Getty ImagesCheck the inside of your microwave, because it's very likely you haven't cleaned it. For first-time clients, microwaves “are usually the dirtiest part of the house,” San Angelo said, because they are the cooking appliance that gets used more than an oven, no matter how big your family is. “When I do a walkthrough with a potential client for the first time and I open the microwave, they usually get a little embarrassed and say, ‘I always forget about the microwave,’” San Angelo noted. How often you should clean your microwave depends on how regularly you use it, San Angelo said, but “if there are splatters on the roof of the microwave, it’s cleaning time.“To clean a microwave quickly, Amber Elise, owner of Bubbles and Buckets in Otsego, Minnesota, suggests popping in a bowl filled with water and lemon juice or some vinegar to boil. “After about five minutes of just sitting in there, everything just wipes out super easily,” Elise said. The Washing Machine Crispin la valiente via Getty ImagesDo you clean the opening of your washing machine? Look out, there's probably dirt and mold. Elise said in her view, the inside of your washing machine is the dirtiest appliance she will clean. It might not look dirty upon first glance, but a bad odor will give it away. “There can be a musty smell that will build up over time if you’re not cleaning it every month,” Elise said. That’s why she recommends using washing machine cleaning tablets to maintain the life of your appliance. And look closely at the openings of your washing machine for signs of grime.“If you have a front-load washing machine, you’ll start to see mold build up on the rubber seal,” Elise said. She recalled opening one top-loading machine for a client and seeing a rim caked with “dirt, hair, stickiness. It was just a whole bunch of grime.” The Oven Iuliia Burmistrova via Getty ImagesThe inside of an oven is out of sight, but it's a major culprit for accumulating grease over time. “In my experience, the part of the house that is the dirtiest is the oven,” said María Guiracocha, a New York City-based house cleaner at Liberty Cleaners, a collective of women organizing for better wages and safer working conditions in domestic cleaning. And in particular, it’s the inside of the oven that gets dirty as food crumbs and grease accumulate, Guiracocha noted, highlighting the oven door and the oven grates as two areas people forget to clean. Don’t ignore your oven stovetop, either. This is a part house cleaners notice too.If you go too long without cleaning up the grease buildup on your stove’s burners and grates, “the grease eventually on your stove top could be permanent,” Elise said. “I’ve had people not clean their oven for years, and it gets real bad.”Cleaning grease and food gunk from your oven isn’t just for aesthetics; it’s for safety, too. More than two-thirds of home cooking fires in the U.S. began with food, fat, and grease catching fire, according to the National Fire Protection Association’s analysis of fire department reports. For ovens that need a deep clean, Elise will use steel wool or a cleaning pumice stone, or she will spray Easy-Off’s cleaning formula and let it set for a few hours before wiping it off. Beyond Cleaning Appliances, Do Regular Tidying Too. House Cleaners Will Thank You. Cleaning goes beyond wiping down surfaces. It also means picking up what’s crowding your floors. House cleaners said you don’t need to pre-clean your oven before they arrive, but moving clutter out of the way is the most helpful action people can do. “If I have to pick up things and put things away, one: I wouldn’t know where they go. And two, it just takes time away from actually doing that deep clean,” Elise said.So if you want to actually be better at cleaning, pick up your dog’s and children’s toys and don’t leave a pile of laundry on the floor. “You don’t need to organize them; we will do that,” Guiracocha said. “When there are young people in houses, there can be piles of clothes on the floor and we don’t know what’s dirty or clean.“Freeing yourself of a disorganized mess is a good habit to adopt, whether or not you work with a house cleaner. Tidying up what’s on the floor and wiping down surfaces after cooking and doing laundry can take a few extra minutes each day, but in the long run, these actions can help extend the life of your appliances and help you avoid hefty cleaning fees.