A Substitute for India Ink for Use in Radiant Heat Pain Threshold Studies

In a previous report (1), attention was called to the stimulatory action on skin surfaces of india ink which previously had been looked upon as an inert blackening agent when used in radiant heat pain threshold determinations. Controlled studies (1) in 50 patients indicated that the application of india ink on normal skin is detectable by the patient in the form of one or more of a variety of sensations. Hence, it was postulated, the effects of india ink may thus prejudice or interfere with determinations of radiant heat pain thresholds. It is the purpose of this paper to describe a material which offers the same desirable qualities as india ink but which is essentially free of the sensory disturbing properties of india ink.