Impact of gut microbiome on skin health: gut-skin axis observed through the lenses of therapeutics and skin diseases

The human intestine hosts diverse microbial communities that play a significant role in maintaining gut-skin homeostasis. When the relationship between gut microbiome and the immune system is impaired, subsequent effects can be triggered on the skin, potentially promoting the development of skin diseases. The mechanisms through which the gut microbiome affects skin health are still unclear. Enhancing our understanding on the connection between skin and gut microbiome is needed to find novel ways to treat human skin disorders. In this review, we systematically evaluate current data regarding microbial ecology of healthy skin and gut, diet, pre- and probiotics, and antibiotics, on gut microbiome and their effects on skin health. We discuss potential mechanisms of the gut-skin axis and the link between the gut and skin-associated diseases, such as psoriasis, atopic dermatitis, acne vulgaris, rosacea, alopecia areata, and hidradenitis suppurativa. This review will increase our understanding of the impacts of gut microbiome on skin conditions to aid in finding new medications for skin-associated diseases.

Rosacea and Diet: What is New in 2021?

OBJECTIVE

Rosacea is a common inflammatory cutaneous condition with a complex yet unknown etiopathogenesis. Diet and certain food items are known to trigger or worsen rosacea symptoms, but conflicting and often inconsistent advice is given to patients regarding this link. We provide an up-to-date literature review on the relationship between rosacea and diet.

METHODS

Using the keywords "alcohol," "diet," "flushing," "food," "inflammation," "rosacea," "skin-gut axis" and "spice" we systemically searched the databases PubMed, MEDLINE and EMBASE for English-language articles in July 2020.

RESULTS

The most frequently reported triggers implicated in rosacea include alcohol, spicy food, cinnamaldehyde-containing foods (e.g., tomatoes, citrus fruits, chocolate), hot drinks, and histamine-rich foods (e.g., aged cheese, wine, processed meats). Some food items appear to play a protective role, such as omega-3, which appears to protect against ocular rosacea. The relationship between certain food items and the subtype of rosacea is varied, with inconsistent results shown in the few studies that examined this. As an example, alcohol worsens flushing and fatty food triggers both erythematotelangiectatatic and phymatous rosacea in susceptible individuals.

CONCLUSION

While several food types appear to be associated with exacerbation of rosacea, there are no recommendations that can be applied to all patients. Further studies are needed to examine the exact link between diet and rosacea subtypes.

Effect of Cigarette Smoke on Gut Microbiota: State of Knowledge

Cigarette smoke is a representative source of toxic chemical exposures to humans, and the adverse consequences of cigarette smoking are mediated by its effect on both neuronal and immune-inflammatory systems. Cigarette smoking also is a major risk factor for intestinal disorders, such as Crohn's disease and peptic ulcer. On the other hand, cigarette smoking is protective against developing ulcerative colitis. The effects of cigarette smoking on intestinal disorders include changes in intestinal irrigation and microbiome, increases in permeability of the mucosa, and impaired mucosal immune responses. However, the underlying mechanism linking cigarette smoking with intestinal microbiota dysbiosis is largely unknown. In this communication, we first review the current knowledge about the mechanistic interaction between cigarette smoke and intestinal microbiota dysbiosis, which include the likely actions of nicotine, aldehydes, polycyclic aromatic hydrocarbons, heavy metals, volatile organic compounds and toxic gases, and then reveal the potential mechanisms of the lung-gut cross talk and skin-gut cross talk in regulating the balance of intestinal microbiota and the interrelation of intestinal microbiota dysbiosis and systemic disorders.