The effect of aging and acute illness on delayed hypersensitivity.

A group of standard antigens (monilia, mosquito, mumps, purified protein derivative [PPD], staphylococcus toxoid, streptokinase-streptodornase [sk-sd] and trichophyton) were applied to 321 normal volunteers, 60 patients admitted to a medical ward, and 41 patients in an intensive care unit (ICU) to evaluate their delayed hypersensitivity skin test response. Eighty-eight per cent of the normal subjects reacted with at least 5 mm. induration to one or more skin tests without any decrease in reactivity occurring with increasing age. In the hospitalized group, only 62 per cent of the ward and 63 per cent of the ICU patients reacted to the same skin tests. All (8/8) anergic ICU patients tested after discharge regained normal reactivity. Acute illness but not increasing age will impair the delayed hypersensitivity skin test response.