L-carnitine: which cosmetic actives to pair it with?

Association No. 1: L-carnitine and arginine.

The combination of L-carnitine with arginine may support the skin’s resilience to oxidative stress. Oxidative stress occurs when free radicals exceed the capacity of antioxidants to neutralise them. In the skin, it may appear as a dull tone, pigmentation marks or premature fine lines.

A study on 36 rats highlighted the synergistic effects of L-carnitine and arginine against neurotoxicity induced by fipronil, a neurotoxic insecticide. The animals were divided into six groups, including one exposed to fipronil alone, and others receiving oral L-arginine (500 mg/kg), L-carnitine (100 mg/kg) or a combination of both for six weeks. Results showed that fipronil exposure caused marked impairment of cognitive function and a reduction in cerebral antioxidant defences. In contrast, groups given arginine and L-carnitine showed significant improvement in all these parameters, suggesting overall neuroprotective action and a protective antioxidant effect. In this study, these amino acids were administered orally, but topical application could also offer antioxidant benefits. Clinical studies in humans would be needed to confirm this.

Combination No. 2: L-carnitine and epigallocatechin gallate (EGCG).

The combination of l-carnitine and epigallocatechin gallate (EGCG), a major polyphenol in green tea, offers a synergistic approach to regulate sebum production and improve skin quality. A randomised clinical trial assessed moisturising creams containing 2% l-carnitine, 5% EGCG or their combination in 90 volunteers with oily skin. Divided into three groups, participants applied the formulas for four weeks, with measurements at weeks 0, 1, 2 and 4. Results showed a significant reduction in sebum across all groups, but the sebum-reducing effect was more pronounced in the combined group.

The combination of these actives improved skin hydration while reducing transepidermal water loss, confirming enhanced skin barrier function. From a mechanistic perspective, L-carnitine stimulates beta-oxidation of fatty acids, thereby reducing their accumulation in sebaceous glands, while EGCG exerts potent anti-inflammatory and antioxidant effects, limiting seborrheic hyperactivity and protecting cells from oxidative stress. In skincare, this combination offers a promising strategy for formulating products for oily and acne-prone skin while maintaining adequate hydration.

Évolution de la sécrétion de sébum. — Changes in sebum secretion.
Source: UDOMPATAIKUL M. et al. Efficacy of an anti-sebum moisturising cream containing 2% L-carnitine and 5% epigallocatechin gallate in seborrhoea: a randomised clinical trial. Journal of Cosmetic Dermatology (2023).

Combination No. 3: L-carnitine, licochalcone A, decanediol and salicylic acid.

The combination of L-carnitine, licochalcone A, 1,2-decanediol and salicylic acid offers an innovative strategy for managing acne-prone skin and preventing relapse. A clinical study in Thailand evaluated this combination in fifty patients with mild to moderate acne after an initial eight-week intensive treatment phase (adapalene 0.1% and benzoyl peroxide 2.5% for eight weeks). After that, for twelve weeks, patients applied a moisturiser containing these four actives to one side of the face and a placebo to the other, twice daily.

The results showed a significant reduction in non-inflammatory, inflammatory and total lesions in the treated group compared with placebo from week 12. No difference in irritation, dryness, or tingling was observed between sides, indicating good tolerance. Mechanistically, licochalcone A has an anti-inflammatory effect by modulating pro-inflammatory mediators and decanediol has antibacterial activity targeting Cutibacterium acnes. The salicylic acid is known for its ability to penetrate deep into pores to unclog them.

Évolution du nombre total de lésions acnéiques au cours du traitement. — Change in the total number of acne lesions during treatment.
Source: Varothai S. et al. A double-blind, randomised, vehicle-controlled study of the efficacy of a moisturiser containing licochalcone A, decanediol, L-carnitine, and salicylic acid to prevent acne relapse in an Asian population. BioMed Research International (2020).

Association No. 4: L-carnitine, hydrolysed collagen peptides, chondroitin sulphate and glucosamine.

Oral L-carnitine is a promising nutraceutical strategy to support skin health when combined with hydrolysed collagen peptides, chondroitin sulfate, and glucosamine. A 90-day, double-blind, placebo-controlled clinical trial in 120 participants tested a supplement based on collagen from hydrolysed fish collagen, vitamins, L-carnitine, chondroitin sulfate, and glucosamine. Results showed a 40% increase in skin elasticity Compared with placebo, skin texture improved as confirmed by histological analysis, with reduced solar elastosis and reorganisation of collagen fibres.

We recommend consulting your doctor before starting supplementation.

Évolution de l'élasticité de la peau des participants. — Changes in participants’ skin elasticity.
Source: Czajka A et al. Daily oral supplementation with collagen peptides combined with vitamins and other bioactive compounds improves skin elasticity and benefits joint function and general wellbeing. Nutrition Research (2018).

Association No. 5: L-carnitine, biotin, panthenol, bisabolol, and α-tocopherol.

This combination of actives could soothe sensitive skin and support care for atopy-prone or irritation-prone skin. A clinical study evaluated the efficacy of a formulation combining L-carnitine, biotin, panthenol, bisabolol and α-tocopherol in participants with eczema. Eczema is a chronic inflammatory dermatosis characterised by red, itchy lesions.

In this study, 30 patients with eczema were assigned to two groups: 20 received the active blend and 10 received a placebo. All applied the product twice daily to the affected areas for three weeks. The clinical assessment covered various criteria (erythema, vesiculation, scaling) rated on a 1–10 visual scale. The results showed a significant improvement in skin lesions and a marked reduction in itch in almost all participants who received the active blend. This restorative and soothing effect is attributed to the anti-inflammatory and moisturising properties of the active ingredients.

Progression of erythema and pruritus associated with eczema.
Source: MESSINESE S. et al. Topical treatment of contact dermatitis with natural active principles. Journal of Plastic Dermatology (2013).

Combination No. 6: L-carnitine and mandelic acid.

It may also be relevant to combine L-carnitine with mandelic acid to enhance its exfoliating properties. A recent study on a porcine skin model evaluated a molecular complex combining mandelic acid with L-carnitine (called M_C complex), comparing it with mandelic acid alone. Different concentrations of mandelic acid (0.1%, 1%, 2%, and 3%) were tested at pH 4.5, that is at physiological pH. The results showed that at this pH, mandelic acid alone lost significant exfoliating power, reaching less than 40% of the efficacy of a positive control (10% gluconolactone at pH 4). In contrast, the M_C complex exhibited a more pronounced exfoliating activity.

Note : It is important to note that these results, although promising, were obtained in a porcine model, not human skin. Additional clinical studies are needed to confirm efficacy and verify the safety of combining L-carnitine and mandelic acid.