This is a very old study and a little hard to interpret based on the limited info, but that last line…
If this were the case the question would be what really causes acne?
Could there also be a correlation with sebum production and the bacteria itself?
What if the bacteria didnt recover or was not there in adequate amounts to begin with?
I’ll have to look at a few more studies of course.
Effect of 13-cis-retinoic acid on sebum production and Propionibacterium acnes in severe nodulocystic acne
https://pubmed.ncbi.nlm.nih.gov/6219631/
Ten patients treated with 13-cis-retinoic acid demonstrated a 70% reduction in sebum excretion on the forehead and cheek. An average reduction of 66% occurred in the 1st month, slowly increased to 70% by the 3rd month, and then remained constant for the final 2 months of therapy. Concomitant with this sebum excretion reduction was a fall in the number of Propionibacterium acnes recovered from both sites. Pretreatment values of 10(4) P. acnes per square centimeter (cm2) fell to 10(3) per cm2 after 1 month and 10(2) after 9 months of therapy. P. acnes was not recovered from six of the ten subjects in the following 3 months and only at levels of 10(2) per cm2 in three subjects. One subject’s P. acnes level was reduced to only 10(4) per cm2. Following discontinuation of therapy, sebum levels and P. acnes counts showed a trend to recover to pretreatment levels within 2 months.
^That was from the 80s.
The following is from 2 years ago,
Medication for severe acne alters skin microbiome
The study’s findings, according to the researchers, suggest that isotretinoin creates a “bottleneck” that selects for beneficial communities of Propionibacteria and other bacteria that appear to be healthy, creating a skin microbial community that reduces the chances of the acne returning, even when normal oil production returns to the skin after treatment stops.
“When you have a bottleneck, you create an opening for other microbes to move in and increase in abundance”
They conclude with this thought,
We hope that our work will inspire future studies to answer these questions and ultimately lead to the development of “prebiotic fertilizers”, strain-selective “weed killers,” and/or probiotic Propionibacterium strains that optimize PSU ecosystems while avoiding antibiotic “collateral damage”.
Propionibacterium that fights acne?