Usog or balis[1] is a Filipino superstition whereby an affliction or psychological disorder is attributed to a stranger's greeting or evil eye hex.
[2] In some limited areas, it is said that the condition is also caused by the stranger having an evil eye or masamang mata in Tagalog, lurking around.
In most other places, to counter the effects of the "usog" the stranger or newcomer is asked to put some of their saliva on the baby's abdomen, shoulder or forehead before leaving the house.
[5] One theory (Kristina Palacio)[6][7] explains usog in terms of child distress that leads to greater susceptibility to illness and diseases.
[9] Technically, the condition results from the child-environment interaction that leads the child to perceive a painful discrepancy, real or imagined, between the demands of a situation on the one hand and their social, biological, or psychological resources on the other.
More than the superstitious folks, researchers dealing with Filipino Psychology say they have observed this phenomenon with regularity and suggest that this be added to the Psychiatric Disorders Handbook DSM-V.[7]