A more recent study of 22 preterm infants randomized to sunflower seed oil daily or control was not as favorable: it found that skin pH actually decreased and transepidermal water loss actually increased in the sunflower group, suggesting that—in this design—sunflower seed oil actually retarded the barrier maturation in premature infants. Because it is a small study and due to the many variables, it is difficult to know what this means in light of the other data, but serves as an important reminder that the answer may not be clear-cut.[vii]
In perhaps a more relevant study, 19 adults were randomized to receive olive oil to one arm versus sunflower seed oil to the other for 4 weeks. Interestingly, the olive oil caused a worsening of the barrier function and even erythema in subjects with and without a history of AD. Sunflower seed oil, on the other hand, did not cause erythema and preserved skin barrier function while actually improving hydration.[i] Although fairly limited, these findings have prompted me to caution patients away from using topical olive oil in favor of sunflower seed oil.
The fact that some botanical oils can be detrimental and others helpful to skin barrier has been demonstrated in the mouse model as well, further bolstering these clinical findings. In a precursor study geared toward identifying safe and inexpensive vegetable oils to enhance epidermal barrier function for neonates in developing countries, several vegetable oils were tested and compared on mouse epidermis. Mustard, olive, and soybean oils were found to significantly delay recovery of epidermal barrier function compared to control and a petroleum-based moisturizer, with mustard oil showing the most detrimental effects of all. Sunflower seed oil, however, significantly improved skin barrier function recovery, with an effect that was sustained 5 hours after application.[vi]
What about in a disease state such as atopic dermatitis (AD)? Here, the evidence points to at least a modest effect for sunflower seed oil. A study of 86 children with moderate AD randomized to corticosteroids with or without a sunflower-oil-containing cream found a significant impact on lichenification and excoriation, decreased corticosteroid use, and improved quality of life compared to the control group.[viii]
Safe, inexpensive, and widely available, sunflower oil seems a reasonable consideration for any patient with impaired skin barrier, so long as there is not a known sunflower seed allergy. While many details are yet to be resolved, including the linoleic vs oleic acid content, the frequency of application, and perhaps the underlying skin issues, sunflower seed oil has been used for quite some time and will likely remain an important ally.