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

Association No. 1: L-carnitine and arginine.

The combination of L-carnitine and arginine shows promise in supporting skin resistance to oxidative stress. As a reminder, cells face oxidative stress when free radicals outnumber antioxidants’ capacity to neutralize them. In the skin, this can manifest as a dull complexion, pigmentation spots, or premature wrinkle formation.

A study in 36 rats highlighted the synergistic effects of L-carnitine and arginine against fipronil-induced neurotoxicity, a neurotoxic insecticide. Animals were divided into six groups, including one exposed to fipronil alone and others receiving either 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 cognitive deficits and reduced cerebral antioxidant defenses. In contrast, groups treated with arginine and L-carnitine showed significant improvement in all these parameters, suggesting broad neuroprotective action and a protective antioxidant effect. In this study, these amino acids were administered orally, but topical application may provide antioxidant benefits. Human clinical trials would be necessary to confirm this.

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

The combination of L-carnitine and epigallocatechin gallate (EGCG), a major polyphenol in green tea, provides a synergistic approach to regulate sebum production and improve skin quality. A randomized clinical trial evaluated moisturizers containing 2% L-carnitine, 5% EGCG, or their combination in 90 volunteers with oily skin. Divided into three groups, participants applied the formulations for four weeks, with assessments at weeks 0, 1, 2, and 4. Results showed a significant reduction in sebum across all groups, with a more pronounced effect in the combined group.

Furthermore, combining these active ingredients improved skin hydration while reducing transepidermal water loss, confirming enhanced barrier function. From a mechanistic perspective, L-carnitine stimulates fatty acid beta-oxidation, reducing their buildup in sebaceous glands, while EGCG exerts potent anti-inflammatory and antioxidant effects, limiting sebaceous hyperactivity and protecting cells from oxidative stress. In skincare, this combination offers a promising strategy to formulate products for oily, acne-prone skin while preserving skin hydration.

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

Association 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 approach to managing acne-prone skin and preventing relapses. A clinical study in Thailand evaluated this combination in 50 patients with mild to moderate acne after an initial intensive treatment phase (0.1% adapalene and benzoyl peroxide 2.5% for eight weeks). After this, patients applied a moisturizer containing these four active ingredients to one side of the face and a placebo to the other side twice daily for 12 weeks.

The results showed a significant reduction in the number of noninflammatory, inflammatory, and total lesions in the treated group compared with placebo by week 12. In addition, no difference in irritation, dryness, or tingling between sides, indicating good tolerance. On a mechanistic level, licochalcone A has an anti-inflammatory effect by modulating pro-inflammatory mediators, and decanediol exhibits antibacterial activity targeting Cutibacterium acnes. The salicylic acid is known for its ability to penetrate 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, randomized, vehicle‐controlled study of the efficacy of a moisturizer containing licochalcone A, decanediol, L-carnitine, and salicylic acid for preventing acne relapse in an Asian population. BioMed Research International (2020).

Association No. 4: L-carnitine, hydrolyzed collagen peptides, chondroitin sulfate, and glucosamine.

By oral intake, L-carnitine is a promising nutraceutical strategy to support skin health. Its effect increases when combined with hydrolyzed collagen peptides, chondroitin sulfate, and glucosamine. A double-blind, placebo-controlled clinical study involved 120 participants who consumed a daily supplement for 90 days based on collagen from hydrolyzed fish, vitamins, L-carnitine, chondroitin sulfate, and glucosamine. The results showed a significant 40% increase in skin elasticity compared to placebo, accompanied by improved skin texture confirmed by histological analysis, which revealed reduced solar elastosis and a reorganization of collagen fibers.

We recommend consulting your physician 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 overall well-being. Nutrition Research (2018).

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

This combination of actives may be beneficial for soothing sensitive skin and supporting care for skin with an atopic tendency or prone to irritation. A clinical study evaluated the efficacy of a formula combining L-carnitine, biotin, panthenol, bisabolol, and α-tocopherol in individuals with eczema. As a reminder, eczema is a chronic inflammatory dermatosis characterized by red, itchy lesions.

In this study, 30 patients with eczema were divided into two groups: a first group of 20 patients treated with the active blend and a second group of 10 patients using a placebo. All applied the product twice daily to affected areas for three weeks. Clinical evaluation covered various criteria (erythema, vesiculation, scaling) measured using a visual scale from 1 to 10. The results showed a significant improvement in skin lesions and a marked reduction in pruritus in most participants who received the active blend. This restorative and soothing effect may be due to the anti-inflammatory and moisturizing properties of the various actives.

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).

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

It may also be relevant to combine L-carnitine with mandelic acid to enhance its exfoliating effect. A recent study on a porcine skin model evaluated a molecular complex of mandelic acid and L-carnitine, called the M_C complex, and compared it to mandelic acid alone. Different mandelic acid concentrations (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 had an exfoliating effect below 40% of a positive control (10% gluconolactone at pH 4). In contrast, the M_C complex displayed a stronger exfoliating activity.

Note : It is important to note that these results, while promising, were obtained on a porcine model rather than a human skin model. Further clinical studies are necessary to confirm efficacy and verify safety of the combination of L-carnitine and mandelic acid.