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Whenever the subject of demodex mites (demodectic rosacea) comes up there is the age old quandary, which came first the demodex or the rosacea? This question was first proposed by Frank Powell, M.D., in an article, Something to Blush About, in the Ivanhoe Newswire. 
The NRS published an article in July 2012 that states, “now there may be some evidence that the “chicken” —Demodex mites — and not the “egg” comes first, according to a recent scientific report.”  This article comments on the work of “researcher Dr. F.M.N. Forton [who] has championed the mite as a key culprit behind the development of the condition, noting it may be the missing link in understanding the onset of subtype 2 (papulopustular) rosacea.”
David Pascoe published an editorial on this subject where he states under the subheading, Dreaming, that “this theory is pretty far fetched.” 
While neither Powell or Forton dogmatically say whether the demodex or the rosacea is first, the evidence points to the demodex mites as coming first, however no one really knows for sure.
The articles written about demodex and rosacea are prolific.  There doesn’t seem to be any end to researchers writing about demodectic rosacea which, without a doubt, more will be coming down the pipeline for us to read about and comment on.
For example, there is a report that two proteins from B.oleronius found on demodex mites may cause an inflammatory response in rosacea patients.  So which comes first the bacteria or the mites? Does it really make any difference? Apparently to some which comes first is very important. Now there is evidence of at least five types of bacteria associated with demodex.
A paper in 2017 continues to explain the quandary. "Many studies have shown higher density of the parasites in diseased inflammatory skin than in normal skin, but whether it is the cause or result of the inflammation remains unclear." 
A paper in 2018 may help to resolve this issue because for the first time it has been discovered that Demodex mites secrete bioactive molecules that reduced TLR2 expression in sebocytes. 
Another paper published in Dermatology and Therapy in 2020 says the following:
Despite these immunologic features, it is unclear whether microorganisms are causative agents or innocent bystanders in rosacea. In other words, does dysbiosis precipitate rosacea, or does the altered cutaneous microenvironment precipitate dysbiosis?" 
So while the jury is still out on this subject, What do you think? Which comes first, the demodex or the rosacea? Does it even matter? The point is that there is evidence that demodectic rosacea needs to be ruled out, especially when you consider the gold standard of rosacea treatment is now Soolantra, which the active ingredient is ivermectin, an insecticide, and Oracea, and treatment using these two, a topical and an oral timed released low dose antibiotic has significant success in treating rosacea. The bottom line is demodectic rosacea is a valid variant of rosacea.
So if you make a choice, which comes first, be careful. Being dogmatic on this subject might get some egg on your face.
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 Powell is quoted as saying: “In other words, which came first: the mites or the rosacea?” study author Frank Powell, M.D., consultant dermatologist at Mater Misericordiae Hospital in Dublin, Ireland, was quoted as saying. “And now there is evidence that it might be the mites.”
Something to Blush About, Medical Breakthoughs, Ivanhoe Newswire, December 11, 2007
 The Chicken, not the Egg?
National Rosacea Society, Thursday, July 5, 2012
 More Demodex Dreaming: Mites are the Chicken?
by David Pascoe, July 24th, 2012
 For a partial list of papers on demodex and rosacea click here
 Positive correlation between serum immuno-reactivity to Demodex-associated Bacillus proteins and Erythematotelangiectic Rosacea.
O’Reilly N, Menezes N, Kavanagh K.
Br J Dermatol. 2012 Jun 18. doi: 10.1111/j.1365-2133.2012.11114.x.
 Iran J Parasitol. 2017 Jan-Mar; 12(1): 12–21.
Human Permanent Ectoparasites; Recent Advances on Biology and Clinical Significance of Demodex Mites: Narrative Review Article
Dorota LITWIN, WenChieh CHEN, Ewa DZIKA, and Joanna KORYCIŃSKA
 Demodex TLR2 Expression in Sebocytes
Demodex Density Count - What are the Numbers?
 Dermatol Ther (Heidelb). 2020 Nov 10;:
Rosacea and the Microbiome: A Systematic Review.
Daou H, Paradiso M, Hennessy K, Seminario-Vidal L