You're in NC, right? They're called "No see-ums." Do you have water nearby? They like water, and they like swarming.
Do you let your dog in and out? They like to swarm around dogs and then follow them into the house and bite you, especially around 4 or 5 and into evening. Even if you don't have a dog, they'll come in. They may also swarm around a porch or patio light.
Their bite hurts more than mosquitoes but the swelling goes away more quickly, I've found.
Wearing insect repellent (yes, while inside) is the only answer, unfortunately. It sometimes helps to cover up bare arms and legs, too.
I don't think the bites are brown spiders, and it won't do any good to fumigate the house, because that doesn't stop them from coming in every time you open the door.