Since oxidative stress is a result of a disbalance of pro- and antioxidants, it is theoretically possible to characterize it from both sides. Really, this is only possible for non-living material. In the human organism, thanks to the antioxidative system, a raised demand of antioxidants is compensated by different means (release from depots, regulation of excretion, de-novo synthesis). Only if this compensation fails the damage begins. Therefore, damage detection is more suitable than antioxidant detection.

A common approach is to determine products of lipid peroxidation (see figure). It is however insufficiently sensitive, since lipids are protected by antioxidants, particularly by vitamin E, and only after their exhaustion the chain reaction of lipid peroxidation begins.

"In contrast to lipid peroxidation the products of which typically appear after a lag time, protein damage by reactive oxygen species takes place directly and immediately. Being independent indices of oxidative stress, protein degradation assays registering alterations in amino acids ... provide many advantages over other techniques. Their most common drawback is the complexity of the applied methods such as radioactive or fluorescent labeling, gel electrophoresis, Western blots, or immunoprecipitation." (Pacifici et al., 1990)

The discovery that oxidatively modified proteins acquire anti-radical capacity was a breakthrough. On this basis and using the chemiluminescence detection principle the new ARAP-KIT series was developed.