Licorice Root May Cool Off the Inflammation
Licorice is well known plant which is able to suppress the conversion of cortisol to cortisone. This effect may significantly help with healing of psoriasis.
The result is that increased levels of cortisol in your blood may suppress the strong immune reactions which are present in psoriasis.
Suppressed immunity leads to less inflammation which may be good if you won’t overdo it.
The study published in 2008 in Journal of Periodontology confirmed that licorice reduces the lipopolysaccharide-induced (endotoxin induced) proinflammatory cytokine production by macrophages and whole blood. 
The researchers concluded that “licorice extract is a potential candidate for the development of a new therapy to prevent and/or treat periodontitis-associated tissue destruction.” 
The licorice extract exhibited potent anti-inflammatory properties, inhibiting the periodontopathogen LPS-induced IL-1beta, -6, and -8 and TNF-alpha responses of macrophages. The licorice extract inhibited the phosphorylation of important macrophage intracellular signaling proteins, including nuclear factor-kappa B p65 nuclear transcription factor and Jun proto-oncogene-encoded activator protein (AP) 1 transcription factor, which are involved in inflammatory signaling pathways. The licorice extract was also a potent inhibitor of the proinflammatory cytokine response in the ex vivo human whole blood model.
Dentistry is well aware that periodontal diseases are caused by specific Gram-negative periodontopathogenic bacteria which cause the destruction of tooth-supporting tissue.
Antibiotics suppress the immune system too
The same authors published the results of the study where they tested the effects of tetracycline antibiotic drug doxycycline on lipopolysaccharide induced inflammation.
There was a significant decrease in secretion of IL-1beta, IL-8 and TNF-alpha by macrophages when the cells were pretreated with doxycycline. The higher dose of doxycycline was needed in order to significantly decrease the production of IL-6.
In a whole blood model the pretreatment with higher dose of doxycycline was needed to significantly inhibit the proinflammatory cytokines production.
The researchers concluded that some of the clinically proven benefits of doxycycline may be related directly to these anti-inflammatory properties. 
In this particular study Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were the bacteria used to induce the inflammatory reaction in macrophages.
“The licorice extract was also a potent inhibitor of the proinflammatory cytokine response in the ex vivo human whole blood model.” 
So why are all those other chronic inflammatory diseases missed and doctors say that they have no known cause?
Maybe the endotoxins coming from inflamed digestive tract are the cause of most chronic inflammatory and degenerative diseases including psoriasis, rheumatoid arthritis, ….
In psoriasis the Streptoccocus pyogenes is suspected as being the major factor in psoriasis mostly in acute cases preceded by strep throat. [6,7]
Licorice extract inhibits lipopolysaccharide induced elevation of pro-inflammatory mediators
In another study the researchers tested the effects of licorice root extract and its active compounds – glycyrrhizic acid, liquritin and liquiritigenin – in mice liver damage and mice brain microglia cells.
All three of the active ingredients in licorice extract inhibited the lipopolysaccharide induced elevation of pro-inflammatory mediators like nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), TNF-alpha, interleukin 1-beta and interleukin-6 in mouse brain microglia cells.
The levels of TNF-alpha, IL-1beta and IL-6 were inhibited by licorice extract in toxin treated mice livers.
The scientists concluded that “licorice extract and its three bioactive components can be applied for the treatment of inflammation-related disorders, such as oxidative liver damage and inflammation diseases” due to its antioxidant properties. 
“Free-radical scavenging activity of licorice extracts and three ingredients were measured by using the DPPH assay. The direct scavenging activity of licorice extract and its ingredients (GA, LQ and LG) on DPPH radicals was expressed as the % of control at 10 mg/mL of licorice root extract and 100 μM of GA, LQ and LG. NAC (N-acetyl cysteine) 10 μM was used as positive control. The results are the means ± SD of three separate experiments.