Aim: to study impact of acute somatic pain on lysozyme activity of different ages rats: newborn, rats after eye opening, month of age rats, adult and old rats. Methods: Lysozyme activity determined before pain irritation and after 2, 30, 60, 120, 180 min using Dorofeychuk’s method in our modification. Pain effect was modeling by electrical stimulation. Results: activity of lysozyme was 0.434±0.01 units in intact newborn rats, it was higher than in adult rats — 0.260±0.01 units (p 0.001) and it was unchanged during the experiment. We found low lysozyme activity in ratsafter eye opening — 0.015±0.003 units and it was stable during the experiment. Month of age rats had diphasic reaction: lysozyme activity was 0.191±0.01 units in intact rats, it increased up to 0.378±0.01 units (p 0.001) in 2 min after painful irritation and it decreased up to 0.113±0.02 units (p 0.001) in 30 min. Lysozyme activity was 0.260±0.01 units. Single-phase reaction was determined after acute painful irritation: increase of lysozyme activity after acute somatic pain up to 0,450±0,014 units (p 0.001). Lysozyme activity was 0.246±0.02 units inblood plasma of old rats. It decreased up to 0.170±0.01 units (p 0.01) after painful irritation and it was 0.387±0.01 (p 0.001) in the end of the experiment. Conclusion: Response on pain irritation has differences in different groups. The common vector of response reaction after pain was the increase lysozyme activity in month of age rats, adult rats, rats after eye opening and old rats. Reaction of increasing lysozyme activity the most expressed in adult rats. The data are considered as a preventive readiness of lysozyme to answer on damage and infection.