Contraindication: A condition which makes a particular treatment or procedure inadvisable. A contraindication may be absolute or relative.

• An absolute contraindication is a situation which makes a particular treatment or procedure absolutely inadvisable. In a baby, for example, aspirin is absolutely contraindicated because of the danger that aspirin will cause Reye syndrome.

• A relative contraindication is a condition which makes a particular treatment or procedure somewhat inadvisable but does not rule it out. For example, X-rays in pregnancy are relatively contraindicated (because of concern for the developing fetus) unless the X-rays are absolutely necessary.

A contraindication is literally contra- (against) an indication, against something that is indicated as advisable or necessary.