- An absolute contraindication is a situation which makes a particular treatment or procedure absolutely inadvisable. In children, for example, aspirin is almost always contraindicated because of the danger that aspirin will cause Reye syndrome.
- A relative contraindication is a condition which makes a particular treatment or procedure possibly inadvisable. For example, X-rays in pregnancy are relatively contraindicated (because of concern for the developing fetus) unless the X-rays are absolutely necessary.
Contraindications often highlight the balance of risk versus benefit of a particular treatment or procedure.