Sometimes Nightmares don’t just wake you up but also leave you with many effects. It can lead to anxiety, disturbed sleep, headache and even fever. The effect depends on how badly it has left you scared and stressed.There are mythological characters like ‘Mare’ or ‘the Old hag’. It is considered that they sit on the sleeper’s chest is when the person has nightmares.Falling of teeth, failing exams, being naked in public, running late for important work or even falling from hights fall into the category of nightmares, any dream that disturbs your emotions and sleep are called nightmares.