A toxic person is anyone whose behavior stresses you out, brings along negative vibes, and leaves you angry with wondering thoughts. Toxicity in people most times is not considered a mental disorder but there could be a personality disorder and underlying mental problems that cause someone to act in toxic ways.
Not a lot of people get to realize when they are breeding toxic people around them. Toxic people are difficult and cause a lot of conflicts anywhere they go. These people can create lots of stress and unpleasantness for you and others, coupled with emotional and physical trauma.
Many times, people who are toxic are dealing with their own stresses, traumas, or pain. To do this, they act in ways that don't present them in the best light and usually upset people around them. If you have a close friend who you are yet to understand why you feel a certain way or become really sad when they are around you or after they leave you might be dealing with a toxic friend.
There are toxic signs to watch out for when you start feeling unease around certain people. Protecting your mental space, peace of mind and stability should be your utmost priority.