Abstract
Determinations of the temperature gradients 1 from the surface of the skin to a depth of 16 mm. in 7 subjects with skin pigment types ranging from blond to negro, before, during and after exposure to varying quantities and wave bands of infrared radiation, indicate that the rise in temperature on the surface is proportional to the quantity of radiant energy and independent of wave length, between 0.75μ, and longer than 5.0μ, and the amount of natural skin pigment. 2 The wave lengths of infrared used were broad bands 0.75μ to 3.0μ, 1.4μ to 5.0μ, 1.4μ to longer than 5.0μ, 3.0μ to longer than 5.0μ and the quantities varied from 0.25 to 1.6 gm. cal. per sq. cm. per min. 3
That there is no relation between the degree of natural pigmentation and the tissue temperatures during infrared irradiation is illustrated by experiments summarized in Table I, which shows tissue temperatures after 5-minute exposures to 1.0 gm. cal. per sq. cm. per min. of infrared (wave length 1.4 to longer than 5.0μ). The differences between these various skin types are no greater than those in a single individual on different days. Other wave bands gave similar results.
On the other hand, when skin areas, artificially pigmented by exposure to a carbon are, are exposed to the same amount of infrared they show somewhat smaller rises in temperature on the surface and at sub-surface levels than do corresponding non-pigmented areas. A typical experiment using 1.0 gm. cal. of long infrared (1.4μ to longer than 5.0μ) is summarized in Table II. We do not believe that the artificial pigment necessarily serves a protective function, but that an increased blood flow (note the higher initial temperatures in the pigmented skin) is responsible.
Get full access to this article
View all access options for this article.