Introduction
Docosahexaenoic acid is an Omega-3 fatty acid renowned for its anti-inflammatory and antioxidant effects. A major benefit of docosahexaenoic acid as a nutraceutical or topical agent is its high safety profile, making it suitable for a wide range of applications. DHA can be incorporated into the phospholipid bilayer of cell membranes to support physiological homeostasis, and act as a precursor for various metabolites with anti-inflammatory and anti- oxidative properties. A well-known metabolite type of DHA is the specialised pro-resolving mediator, which works to stop excessive or prolonged immune responses following acute inflammation.

DHA supporting the function of our skin as a protective barrier
Our skin acts as a protective barrier against damaging agents and factors in the outside world. One of these damaging factors is somewhat paradoxically also something that is essential for our health: sunlight. Even though sunlight is important in supporting our health, the UV radiation in sun rays poses a constant risk factor to the integrity of our skin cells. UV radiation can cause oxidative and inflammatory damage called photoaging (damage sustained through exposure to light) and even skin cancer. It can also break down collagen, a protein critical for the structural integrity of our cells, which causes a loss of skin elasticity that presents itself as wrinkles. Oral supplementation of mice with DHA-rich krill oil has been reported to protect against the UV radiation-induced decrease in skin collagen, together with improvements in levels of wrinkling and skin hydration (J. Kim et al. 2023). 

Although dietary intake provides the main source of DHA in our body, the anti-oxidative and anti-inflammatory properties of DHA can be realised through topical application as well. This is especially relevant for the skin, both in health and disease. Topical application of DHA may enhance its uptake in the skin compared to dietary intake, which can enhance the anti- oxidative and anti-inflammatory effects. This method of DHA administration has therefore been chosen in many studies by a prominent research group led by Dr. Surh of the Seoul National University. Using animal models replicating human skin, the laboratory of Dr. Surh has proven over the years how topical DHA administration protects against UV-B damage and skin cancer (S. H. Kim et al. 2023; Rahman et al. 2011; Yum et al. 2017). Using a hairless mouse model, this laboratory has proven how the topical administration of a DHA metabolite is able to reduce the levels of markers for oxidative stress following UV-induced skin damage.
Moreover, using similar models, the research group showed that topical DHA administration prior to exposure to damaging UV radiation can protect against the
activation of inflammatory and oxidative stress mechanisms in the skin (Rahman et al. 2011; Yum et al. 2017).

As these treatments aim to prevent skin damage and cancer development following UV damage, ethical constraints do not allow the same study setup being tested in a clinical trial. This is due to the fact that study participant would have to be exposed to potentially cancer- causing levels of UV-radiation. Furthermore, clinical intervention trials are not suitable to investigate general ageing of the skin in humans, as this is a process of accumulating damage and increasing inflammatory reactions over many years. Nevertheless, studies using human skin cells report that DHA resolves inflammatory reactions and improves its barrier function (Jia et al. 2019; Serini et al. 2019).

A commonality between general ageing of the skin (for example through UV damage) and skin conditions and is the similarity of inflammatory mechanisms that are at play. Over the years, our skin accumulates damage from constant exposure to harmful agents and radiation from sunlight; this coincides with a general increase in levels of inflammation that occurs with age, referred to as ‘inflammaging’. As with protecting against inflammation due to UV damage, research has put forward the protective role of DHA against skin conditions where inflammation plays a central role.

Positive role of DHA in conditions of the skin
Many skin conditions are characterized by persistent inflammatory reactions, such as psoriasis, acne, and eczema. The symptoms of these conditions lead to a significant decrease in the quality of life; the altered aesthetics can be a large burden for affected individuals. Perhaps not surprisingly, a deficit in anti-inflammatory Omega-3 acids is associated with certain skin conditions (Guertler, Fiedler, et al. 2024; Kim et al. 2025; Myśliwiec et al. 2017). Research has shown that DHA supplementation has a positive influence on skin health in these conditions, as detailed below. 

In persons with psoriasis, higher relative levels of DHA are associated with a lower psoriasis severity score (Myśliwiec et al. 2017). Furthermore, supplementation of human skin cells with DHA can cause a reduction in the abnormal proliferation of these cells that causes psoriasis (Morin et al. 2021). In persons with acne, dietary supplementation with DHA has been shown to reduce the number of inflammatory and non-inflammatory lesions (Guertler, Neu, et al. 2024; Jung et al. 2014). Another prevalent condition of the skin wherein DHA can play a positive role is atopic dermatitis, commonly referred to as eczema. In this skin condition, oral supplementation with DHA improves dermatological scores of eczema severity in people with this condition (Koch et al. 2008).

Taken together, scientific studies such as those mentioned above show us how DHA can counter inflammation and oxidative damage in the skin, both of which play a central role in skin conditions and general ageing of the skin.

References
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