Petechiae are similar to purpura. Both are caused by tiny spots of bleeding under the skin. The main difference is that petechiae are less than 4 mm wide. They are flat and not painful or itchy, but they may be mistaken for a rash.
One way to tell the difference between petechiae and a rash is that a rash will turn pale when you push on it; petechiae will not. Low platelets or medications can cause petechiae, as can some severe conditions, including endocarditis, infection, and leukemia.

This site offers information designed for educational purposes only. You should not rely on any information on this site as a substitute for professional medical advice, diagnosis, treatment, or as a substitute for, professional counseling care, advice, diagnosis, or treatment. If you have any concerns or questions about your health, you should always consult with a physician or other healthcare professional.