Health Boosters are jet injectors that fully heal the player and also permanently increase maximum health by 5 health points (up to 199 maximum health points). In the multiplayer modes of F.E.A.R. First Encounter Assault Recon and F.E.A.R. Perseus Mandate, each killed player drops a different kind of Health Booster, which heals 40 health without increasing maximum health. They are blue in color, and give off a glow in dark areas. This can be helpful to locate them in areas the player normally wouldn't go while in a hurry.
F.E.A.R. First Encounter Assault ReconEdit
In F.E.A.R., if the Point Man reaches the maximum health of 199, the Health Boosters will continue to heal him if he's injured, but will not increase his maximum health past this point.
Health Boosters are also found in F.E.A.R. Perseus Mandate and F.E.A.R. Extraction Point. They work the same as in F.E.A.R., though there are not as many to be found in Extraction Point and Perseus Mandate as there were in F.E.A.R.
In F.E.A.R. 2: Project Origin, Health Boosters are replaced by Medical Injectors. They are red in color, and only provide healing, not boosting max health.