Effective moisture retention and a radiant and luminescent skin tone are key markers of healthy and beautiful skin. In recent years, accumulating data has suggested that the microbiome present on the skin can play a key role in providing these benefits to the skin. In particular, the balance between the beneficial and detrimental bacteria. In healthy skin, the balance is tipped towards beneficial bacteria species or strains, limiting the growth of detrimental strains - resulting in radiant and well hydrated skin. Substances with prebiotic properties can support the growth of beneficial bacteria, allowing them to better compete with detrimental bacteria.
Dragon fruit (hylocereus undatus) is a super fruit, rich in polysaccharides previously demonstrated to have prebiotic effects on gut bacteria. In the present study, a hylocereus undatus fruit extract was tested in a competitive growth assay comparing growth rates of staphylococcus epidermidis and s. hominis, representing beneficial bacteria, with those of S. aureus and P. Acnes, representing detrimental bacteria. In this model, the hylocereus undatus fruit extract was shown to support the growth of s. epidermidis and s. hominis, while limiting the growth of s. aureus and p. acnes. 
In parallel, a clinical study was conducted on 26 volunteers, vs. placebo (in a split-face design, where each volunteer provides a direct comparison). In this subject, imaging under UV light (Visia) showed that the hylocereus undatus fruit extract significantly reduced the appearance of porphyrins, indicating a limiting effect on p. acnes growth. In addition, the same study showed that the extract delivered improvements in skin radiance (by colorimetric evaluation) and skin barrier function (by TEWL measurement).
The above results indicate that a hylocereus undatus fruit extract may positively influence skin microbiome balance, and thereby deliver significant skin health and beauty benefits.

Skin radiance improvements with Hylocereus Undatus fruit extract influencing skin microbiome.