Although the exact pathology of rosacea is not yet clear, some evidence suggests that vitamin D and its involvment in modulating the immune system is indicated. Vitamin D and its analogues have previously been shown to be associated with other chronic skin conditions such as psoriasis, atopic dermatitis, vitiligo and acne.
One study1 examined the relationship between serum vitamin D levels and the clinical features of rosacea in a population of 44 rosacea patients and 32 healthy controls. Results showed that, overall, the mean levels of vitamin D were significantly higher in the rosacea group compared with the control group, at 21.4 ng/ml versus 17.1 ng/ml. The study concluded that increased vitamin D levels may act as a risk factor for the development of rosacea.
Researchers have also pointed out that raised vitamin D levels may be the result of excessive sun exposure, a factor known to trigger rosacea.
Another study3 has shown that the skin of people affected by rosacea has a significantly increased expression of cathelicidin, an antimicrobial peptide that increases local immune reaction. Furthermore, there is an increased activity of local skin proteases, leading to the production of cathelicidin peptide fragments that trigger inflammation. This inflammation is further enhanced by UV irradiation and microbes which increase levels of vitamin D(3) and the activation of the toll-like receptors (TLRs).
Retinoids, azelaic acid and doxycycline are all known to inhibit the expression of skin proteases and TLRs, and may provide a means of reducing this inflammation cascade.