Hydrogen Peroxide Topical Solution, 40% (w/w) for the Treatment of Seborrheic Keratoses

A Review

Emily C. Murphy, BS; Adam J. Friedman, MD


Skin Therapy Letter. 2020;25(1):1-4. 

In This Article

Application and Mechanism

HP40 is applied by a healthcare professional with a single use pen that includes 0.7 mL of 40% H2O2 and can treat about seven SKs.[24] According to the manufacturer's instructions, the tip of the pen is pressed to an SK and the solution is applied in a circular motion for about 20 seconds. This process is repeated up to three additional times per SK with 1 minute between each application. After 3 weeks, the SK can be re-treated if satisfactory clearance was not achieved.

The mechanism by which HP40 destroys keratinocytes is not fully elucidated, but is thought to involve H2O2's oxidizing power[21] as both a direct oxidant and indirect oxidant through the formation of hydroxyl radicals.[25] When this oxidative stress overwhelms the antioxidant properties of the skin, H2O2 can lead to cellular destruction by damaging proteins, lipids, and nucleic acids.[25] Applied at a supra-physiologic concentration, a portion of the HP40 dose likely diffuses through the stratum corneum (SC) and into the epidermis.[20,21] Free radicals generated by H2O2 can then induce apoptosis or necrosis of seborrheic keratinocytes among other cell types (Figure 1). Given this mechanism, HP40 should not be applied to open or infected SKs; without an intact SC to act as a barrier, high concentration H2O2 can cause rapid death of adjacent cells (Figure 1).[26] Additionally, HP40 should not be applied within the orbital rim where contact with H2O2 can cause corneal injury.[24]

Figure 1.

Proposed mechanism of HP40. When HP40 is applied to raised, intact SKs (1), some of the dose diffuses through the SC and into the epidermis where it forms hydroxyl radicals (OH•). The skin has an antioxidant system to protect against damage by free radicals, but when H2O2 is applied at supra-physiologic levels, as done with HP40, hydroxyl radicals can overwhelm this system and cause cellular apoptosis or necrosis. If HP40 is applied to open SKs (2) where the SC is not present to act as a barrier, H2O2 can cause more extensive cell death (signified by the thicker arrow pointing to apoptosis or necrosis with Open SKs than with Intact SKs), potentially leading to sequelae such as erythema, vesicles, or purpura.26,27