Science Models
Science Fair Projects

Published on Sep 05, 2023


The objective: The objective is to determine which acne medications are the most effective in inhibiting the growth of Propionibacterium acnes, over-the-counter or prescription.


The active ingredients of two prescription antibiotics, three over the counter acne medications and two plant extracts were tested in vitro in duplicate two separate times against P. acnes.

The bacterium was incubated under anaerobic conditions in the presence of disks containing the study medications and a control disk.

The diameter of each inhibition zone was measured to the nearest millimeter and recorded.


Tetracycline was the most effective, with an average inhibition zone of 46.25 mm, followed by Clindamycin with a 45.5 mm inhibition zone. Surprisingly, Oregano oil had the third largest inhibition zone of 31.25 mm.

Benzoyl peroxide 10%, Benzoyl peroxide 2.5%, the equal mix of Tea Tree oil and Oregano oil followed with inhibition zones of 24.75 mm, 23 mm, and 19.67 mm zones, respectfully.

Lastly, with inhibition zones of 0 mm were the control, Salicylic acid, and Tea Tree oil.


The prescription acne medications are the most effective in vitro against Propionibacterium acnes.

This project compares the in vitro effectiveness of prescription verses over- the -counter acne medication aginst Propionibacterium acnes.

Science Fair Project done By Lindsey N. Drake