Skin plays not only a physical role as the shelter for the living body
but also many important biological roles. Observing the out- or insid
e of skin by the photoacoustic (PA) method, new information that is di
fficult to measure can be detected. We have attempted to measure the p
ercutaneous absorption of chemical substances in order to investigate
the effect and the toxicity of medicinal compounds. To do this, we had
to develop a PA cell that could detect a chemical substance on skin w
ith high sensitivity and accuracy. Several such investigations have be
en reported; however the conventional open-ended PA cells had unfavora
ble signal to noise ratio (SIN) and sensitivity. We have reported the
development of percutaneous absorptiometry using the laser PA method.
A series of in vitro and in vivo percutaneous absorptiometries was per
formed. As a result, if was concluded that this PA method is applicabl
e to percutaneous absorption in situ.