Formulation Science

The Skin Diary’s ethos is built on a simple and highly effective principle: Protect, Repair, Restore. Our ingredients and formulations are carefully designed to protect against UV and environmental damage, repair existing cellular and DNA damage and restore optimal barrier and cell function.

Thoughtfully Chosen Ingredients

Our ingredient formulations are selected based on our clinical understanding of skin biology and on scientific evidence. Despite many individual ingredients having some impressive research, we stand by the belief that final formulation determines real-world efficacy. That’s why we go beyond theoretical efficacy, and instead test our formulations as a complete, finalised product. 

As a consultant dermatologist-led brand, we actively invest in testing our products further, regularly reviewing research and the development of testing methods. With a team consisting of pioneering skin experts, we’re committed to consistently improving and understanding the research behind skincare to give you the best in skin health science. 

We categorise our ingredients into functional groups corresponding with specific biological targets in skin ageing.

Here’s how they work:

Protect

Antioxidants defend against oxidative stress, while next-generation encapsulated UV filters shield the skin from UVA/UVB and environmental damage.

Antioxidants

Oxidative stress is one of the earliest and most damaging drivers of skin ageing. It accelerates DNA damage, collagen breakdown, pigmentation, and cellular senescence — often before any visible signs emerge. We take a precision approach to antioxidant therapy, combining select actives to intercept this damage at multiple levels.

Some of the key antioxidants we draw on across the range include:

Vitamin C & Vitamin E are two of the most abundant antioxidants in the outermost layer of your skin — the stratum corneum. Together, they form a powerful defence system: but these get depleted by UV, pollution, and ageing. vitamin C and E help strengthen your skin’s natural defences.

Vitamin C (ascorbic acid) helps neutralise free radicals, supports collagen production, and boosts the skin’s ability to repair oxidative damage. 

Vitamin E (tocopherol) protects cell membranes from lipid peroxidation and works synergistically with vitamin C — vitamin C actually helps regenerate vitamin E, restoring its antioxidant power after it's been used up.

Carotenoids: A carotenoid is a naturally occurring pigment found in plants, fruits, and vegetables — it gives them their vibrant red, orange, and yellow colours. In the skin, carotenoids act as antioxidants, helping protect cells from oxidative stress caused by sunlight, pollution, and ageing. Eg Lycopene (from tomatoes), Beta-carotene (from carrots), Lutein and zeaxanthin (from leafy greens)

We chose Lycopene (from Tomato Skin) because of the molecular and in vivo evidence that lycopene as a compound has the ability to reduce UV photodamage.

  • Grether-Beck S, Marini A, Jaenicke T, Stahl W, Krutmann J. Br J Dermatol. 2017 May;176(5):1231-1240. doi: 10.1111/bjd.15080.
  • Rizwan M, Rodriguez-Blanco I, Harbottle A, Birch-Machin MA, Watson RE, Rhodes LE. Br J Dermatol. 2011 Jan;164(1):154-62. doi: 10.1111/j.1365-2133.2010.10057.x.

Polyphenols

You’ll notice an abundance of ingredients derived from botanicals are used in skincare— berries, tomato skin, green tea, even tropical ferns. Their inclusion is rooted in emerging scientific evidence showing that bioactive compounds in plants can deliver measurable benefits to skin health.

From polyphenols to flavonoids, these plant-derived compounds offer antioxidant, anti-inflammatory, photoprotective, and even gene-regulating properties. Increasingly, research is also exploring their role as senotherapeutics — ingredients that target and modulate cellular senescence, a key driver of skin aging.

In fact, many of these compounds — including quercetin and fisetin — are currently being studied by some of the world’s leading skin ageing scientists. These research centres are investigating how plant bioactives might slow or even reverse aspects of biological ageing by influencing cellular pathways like DNA repair, oxidative stress response, and the clearance of senescent cells.

Bilberry Extract (Vaccinium myrtillus):
Bilberry is rich in anthocyanins, a subclass of flavonoids responsible for its deep purple pigment and potent antioxidant activity. It also contains high levels of quercetin, a powerful flavonol known for its anti-inflammatory properties.

  • Benefits: Neutralises free radicals, supports microcirculation, reduces oxidative stress linked to photoageing.
  • Evidence: Calò R, Marabini L. J Photochem Photobiol B. 2014 Mar 5;132:27-35. doi: 10.1016/j.jphotobiol.2014.01.013.
  • Clinical relevance: One of the star ingredients in Night Repair Therapy, bilberry plays a role in modulating the skin’s response to UV damage and promoting repair.

While not all plant extracts are created equal, those supported by mechanistic and clinical data deserve their place in evidence-based skincare. With a growing body of research into epigenetics, antioxidant biology, and senotherapeutics, these actives are no longer fringe; they’re at the forefront of next-gen skincare.

UV Filters

SPF 50 & PA++++ Ultra high UVA1 protection are what you would expect from dermatologist-designed sun protection.


Encapsulated filters go beyond that, these are next-generation technology which are enveloped in a W-O-W shell creating 1 µm microparticles.

This not only prevents them penetrating skin layers, minimising skin irritation, but it also makes them incredibly robust and stable.

The double-shell structure enhances stability but it is also negatively charged meaning it creates a perfectly even layer of protection on your skin with none of the flocculation (clumping) that can occur with other filters so there is even spreadability.

  • Prevent aggregation — allowing even spread across the skin
  • Improved filter stability (Many common UV filters are labile, meaning they are chemically unstable when exposed to sunlight — especially UV radiation. This instability can reduce their protective effect over time)
  • Reduce irritation and absorption — staying on the skin surface instead of penetrating it
  • Provides consistent and broad-range protection from UVA & UVB (280–400 nm)
  • Demonstrates stable SPF retention over extended wear
  • Offers a light, non-greasy, non-sticky finish, suitable even for sensitive skin

Repair

Retinoids, peptides, niacinamide and DNA repair enzymes actively support collagen stimulation, DNA repair, and cellular regeneration.

Retinoids

 There’s no mistaking dermatologists’ deep respect for retinoids — widely regarded as one of the most effective ingredients in modern skincare. Our founding dermatologist, Professor Chris Griffiths OBE, has studied retinoids for over three decades and helped establish their role in both clinical dermatology and cosmetic skin ageing.

Retinoids are a family of vitamin A derivatives known to improve skin texture, tone, fine lines, and overall skin quality. Within this family, we focus on retinyl esters which have exceptional stability and gentle efficacy.

Prescription retinoic acid, acts directly on skin receptors but often causes irritation and barrier disruption, the other retinoids follow a gradual conversion pathway to the active form that drives collagen production and cell renewal over time. This stepwise transformation allows for slow, sustained activity that is kind to the skin, especially for those prone to sensitivity.

Thanks to their chemical stability, retinyl esters remain potent over time and are well-suited to long-term use. When used consistently, they deliver visible improvements in fine lines, elasticity, and uneven pigmentation, while supporting a healthier, more resilient skin barrier.

Peptides

Peptides are short chains of amino acids that act as cellular messengers, helping the skin repair, strengthen, and regulate itself. They play targeted roles in boosting collagen production, calming inflammation, reducing pigmentation, and improving elasticity. Peptides play a key role in our formulations.

Palmitoyl Pentapeptide-4 (also PPtk) — a signal peptide clinically shown to stimulate collagen synthesis, enhance skin firmness, and visibly reduce fine lines.

DNA Repair Enzymes

80% of skin ageing is the result of UV exposure. Our skin repairs as much of this damage as it can but Our skin’s natural DNA repair capacity declines with age. By supplementing repair enzymes, we target damage at the root.

  • Photolyase: A light-activated enzyme that repairs UV-induced DNA damage (CPDs).
  • Endonucleases: Support nucleotide excision repair pathways to reverse DNA lesions before they cause cell dysfunction.

Niacinamide

Niacinamide (Vitamin B3) is a multifunctional active that fits across all three categories — but its primary role in repair. It enhances cellular energy and reduces inflammation.

Restore

Bio-identical lipids, medium-chain hyaluronic acid, glycerin, plant oils, and squalane replenish the skin barrier, restore hydration, and improve elasticity for a healthier, more resilient epidermis.

Medium-Chain Hyaluronic Acid (M-HA)

With a molecular weight between 50–300 kDa, M-HA penetrates more deeply into the epidermis than high molecular weight forms.

  • It binds water in the extracellular matrix, providing deep hydration and improving skin elasticity.

  • Critically, M-HA interacts with the CD44 receptor, a key player in cell proliferation, migration, and wound healing — functions that decline with age and immunosenescence.

Glycerin

A well-established humectant that draws water into the stratum corneum from the environment and deeper skin layers.

  • Helps maintain osmotic balance, preventing keratinocyte shrinkage and supporting barrier repair.
  • Supports aquaporin-3 expression, enhancing intercellular water transport and improving skin smoothness and suppleness.

Bio-Identical Lipids

 Mimic the natural lipid matrix of the stratum corneum, reinforcing barrier function.

  • Replenishing these lipids improves TEWL (transepidermal water loss), reduces inflammation, and supports recovery in aged or compromised skin.

  • Essential for restoring the lamellar bilayers that are often disrupted in photoaged or barrier-damaged skin.

Plant Oils (e.g., jojoba, almond.)

Rich in essential fatty acids (linoleic, linolenic acid), phytosterols, and antioxidants.

  • Support lipid barrier restoration, reduce surface inflammation, and offer anti-microbial properties.

Squalene (or Squalane, depending on format)

A naturally occurring emollient found in human sebum; bio-compatible and well-tolerated.

  • Acts as a lipid replenisher, restoring suppleness to dry or depleted skin.
  • Has anti-inflammatory and antioxidant properties, and improves absorption of other actives by enhancing lipid fluidity in the skin barrier.