Absorption (skin)

Along with inhalation, ingestion and injection, dermal absorption is a route of exposure for bioactive substances including medications.

[2] Though small amounts of chemicals may enter the body rapidly through the glands or hair follicles, they are primarily absorbed through the epidermis.

Thus lipid-soluble chemicals make it through the layer and into the circulation faster, however nearly all molecules penetrate it to some minimal degree.

[5][6] Absorption of chemicals in municipal water and dental products such as VOC (Volatile Organic Compounds), TTHM (Total Trihalomethanes), fluoride and disinfectants is a major exposure to environmental health hazards.

Certain solvents like dimethyl sulfoxide (DMSO) act as carriers and are frequently used to transport medication through the skin.

Dermal dosage forms include: liniments, braces, lotions, ointments, creams, dusting powders, aerosols, and transdermal patches.

Slower skin absorption versus oral or injectable may allow patches to provide medication for 1 to 7 days.

[14] For instance nitroglycerin given transdermally may provide hours of protection against angina whereas the duration of effect sublingually may only be minutes.

The transit of chemicals into the skin can be directly measured using non-invasive optical techniques with molecular specificity, such as Confocal Raman Spectroscopy.

A single measurement sequence can thereby establish a snapshot profile of chemical concentration against depth inside the skin.

Since modern Raman Spectrometers exhibit extremely high SNR, in-vivo absorption testing in human skin is possible on a scale of a few minutes or hours.

Biomonitoring, such as taking urine samples at intervals, from workers exposed to chemicals may provide some information but it is difficult to distinguish dermal from inhalation exposure using this method.

[4] The Franz Cell apparatus consists of two chambers separated by a membrane of animal or human skin.

The bottom chamber contains fluid from which samples are taken at regular intervals for analysis to determine the amount of active cells that has permeated the membrane at set time points.

Models are used in some instances to predict the amount of exposure or absorption and to assess public health hazards.