Table 1

Absorption of products following topical use

Benzoyl peroxideNot detected in serum. Small amounts of the metabolite benzoate are absorbed and easily eliminated2,3
TretinoinEndogenous vitamin A levels remained unchanged after repeated applications of 0.05% tretinoin4
Clindamycin phosphateNot detected in plasma5
ErythromycinNot detectable in serum6
Salicylic acidUndetectable from up to 25% in normal skin (depends on vehicle, pH, strength, and quantity applied). Levels might be higher when applied to damaged skin7
Glycolic acidUp to 27% is absorbed into the skin, dependent on pH, concentration, and time8
Hydroquinone35%–45.3% is systemically absorbed through the skin9
Sunscreens (oxybenzone, octocrylene, octisalate)Below the limit of detection up to 8.7%10,11
Dihydroxyacetone (self-tanning)Estimated at 0.5% systemically available12
Depilatory products
  • Thioglycolic acidHuman studies on systemic absorption of thioglycolic acid have not been conducted
  • Sodium, calcium, and potassium hydroxideThe amount found in consumer products, which would come in contact with skin, would be negligible compared with daily dietary intakes of these ions and therefore would not increase serum levels13
Hydrogen peroxide (skin bleaching)In an in vitro study involving human skin, hydrogen peroxide was detectable in the dermis only after the application of high hydrogen peroxide concentrations for several hours14