A fatty acid transporter — not just for muscles

Carnitine is a naturally occurring amino acid derivative involved in energy metabolism. Why does this substance draw attention beyond the metabolic disease community, including dermatologists? Canadian researchers addressed this question in a systematic review published in 2026: the authors pooled 59 publications on topical and systemic use of carnitine and its biomarker potential. No meta-analysis of their own was performed; clinical trials sit alongside experimental data and carry a different weight of evidence [1].

Carnitine is synthesized in the body from lysine and methionine and also comes from food. It is a water-soluble compound containing a quaternary ammonium group and a carboxyl group; the physiologically active form is L-carnitine, or levocarnitine. Its key function is carrying long-chain fatty acids into mitochondria for β-oxidation and energy production. Acetyl-L-carnitine and propionyl-L-carnitine are biologically active derivatives, but they are not interchangeable drugs with an identical evidence base.

Medicine's interest in carnitine goes beyond correcting a deficiency. It is being studied in cardiovascular disease, insulin resistance, liver disease, peripheral neuropathy, and in patients on dialysis. The rationale for this broad search is the combination of a metabolic function with reported antioxidant, anti-inflammatory, and cytoprotective properties. Yet the existence of these mechanisms does not establish clinical efficacy in any of the listed conditions [2].

From medical indications to promises on the label

Carnitine is used in dietary supplements — both as a stand-alone ingredient and as part of multi-ingredient products, including those aimed at people who exercise [2]. Marketing for such products often claims improved endurance, faster recovery and weight loss. Here it matters not to conflate the biochemical function of the substance with the result of taking it: a role in fatty acid oxidation does not in itself prove a reduction in body fat.

Medicines containing levocarnitine are a separate category. Their medical indications include treatment of primary systemic carnitine deficiency and of secondary deficiency in certain inherited metabolic disorders, and, for some intravenous products, prevention and treatment of deficiency in patients with end-stage renal disease on dialysis. The exact list of approved indications depends on the country and the dosage form; prescribing should follow the local label.

It is essential to distinguish replacement therapy for carnitine deficiency from using carnitine to alter metabolism in a person without an established deficiency. Levocarnitine is used as a medicine in specific medical conditions. That in itself does not support advertising claims that L-carnitine helps with weight loss or skin rejuvenation, and it does not prove that dietary supplements or skincare products containing it work [3].

Interest in carnitine in dermatology and aesthetic skincare runs along several lines.

In dermatology:

• regulation of sebum production;
• tolerability of acne treatment;
• tissue repair;
• metabolic changes in dermatoses.

In aesthetic skincare:

• pigmentation;
• cellulite;
• age-related skin changes.

The review reflects a broadening research agenda, but it cannot be used to gauge sales growth or consumer popularity of carnitine.

One ingredient, several routes

Topical L-carnitine is studied mainly in products for oily and acne-prone skin, often at concentrations of 1–5%. It is frequently combined with licochalcone A, salicylic acid, epigallocatechin gallate, and other ingredients. The formula as a whole therefore needs to be assessed, not just the presence of carnitine in it.

Oral use in dermatology studies is mostly about supporting patients during systemic therapy — for example, corticosteroids, isotretinoin, or vismodegib. That is a different line of inquiry and does not confirm the efficacy of a topical product. The review also notes intravenous administration of carnitine derivatives, particularly in studies of vascular disease; those results cannot be carried over to injectable aesthetic protocols.

Let us look at three distinct roles: an ingredient in products for aesthetic goals, a potential adjunct during treatment, and a biomarker candidate. Each needs its own evidence: better tolerability of therapy does not prove rejuvenation, and a metabolic association does not yet make a diagnostic test.

Role 1. An ingredient in products for aesthetic goals

Work in this area covers skin oiliness, pigmentation, cellulite, and age-related changes. What these studies share is not a proven universal action of carnitine but its presence in the products tested. It is important to keep apart results for topical skincare, for an oral multi-ingredient supplement, and for a cell culture experiment: they answer different questions. They cannot stand in for one another.

The sebaceous gland as a target

In a study by Detudom et al. (2023), 90 adults with oily or combination skin used one of three formulas for four weeks: 2% L-carnitine, 5% epigallocatechin gallate, or the two combined. Sebum secretion fell by 34.84%, 41.36%, and 43.45%, respectively. But the comparison was between active formulas, not between carnitine and placebo: a change from baseline cannot automatically be credited to a single ingredient [4].

A study by How et al. (2023) matters for practice as well: 56 patients with mild to moderate acne received adapalene 0.1% plus one of two sunscreens — one with L-carnitine and licochalcone A, the other with niacinamide. Efficacy did not differ significantly by lesion count, but the first formula was better tolerated, with less dryness, burning, and stinging [5]. That supports the studied formula as an adjunct to therapy, not the independent action of carnitine.

Pigmentation: a signal, but an ambiguous one

Results for post-inflammatory hyperpigmentation are inconsistent. In a randomized study of 29 people with acne from mild to severe, Wanitphakdeedecha et al. (2020) assessed a cream containing L-carnitine, licochalcone A, and decanediol alongside intense pulsed light (IPL) photodynamic therapy. The cream and its vehicle were applied to opposite sides of the face for 10 weeks. The active side showed faster resolution of acne lesions, a lower melanin index, and improvement in post-inflammatory hyperpigmentation [6].

In another study — a randomized, double-masked, split-face trial by Puaratanaarunkon and Asawanonda (2022) — 60 participants with phototypes III–IV were compared after a single picosecond laser session: a sunscreen with L-carnitine and licochalcone A versus a product with the same UV filters but without those ingredients. Over 6 weeks, there was no significant between-side difference in post-inflammatory hyperpigmentation, only a trend toward less pigmentation on the active-formula side [7].

How et al. (2023) also reported improvement in post-acne pigmentation with both sunscreens used alongside adapalene, with no significant difference between them [5].

All three studies involved multi-ingredient products, not carnitine monotherapy. These data provide no grounds to promise prevention of pigmentation after procedures.

Cellulite: objective measurements versus how participants felt

With cellulite, it is especially important to separate objective measurements from subjective assessment. Nasrollahi et al. (2015) ran a randomized, double-blind, placebo-controlled trial with right–left comparison: 12 healthy women aged 22–58 with mild to moderate cellulite on the thighs and buttocks applied an active cream and a placebo for two months. According to the review, the active product contained 5% L-carnitine, coenzyme A, caffeine, ginger extract, and other ingredients.

There were no significant between-side differences in thigh circumference, subcutaneous fat thickness, or dermal characteristics. About 90% of participants rated their satisfaction with the active product at 5 or higher on a 0–10 scale, yet ratings on the placebo side were similar. This result therefore cannot be presented as confirmation of a pronounced cosmetic effect [8].

Other studies recorded objective changes, but they cannot isolate carnitine's contribution. Roure et al. (2011) studied 78 women using a cream with caffeine, carnitine, forskolin, retinol and tetrahydroxypropyl ethylenediamine. Body circumferences decreased over 12 weeks, but the results are for the whole formula [9].

Escalante et al. (2019) studied a lotion with aminophylline, caffeine, yohimbe, L-carnitine, and gotu kola. Seven of the 10 women completed the study: for 28 days they applied the active product to one thigh and placebo to the other while following a hypocaloric diet and a walking program. Reductions in thigh circumference, skinfold thickness, and fat mass were greater on the active side. Diet and exercise were the same background for both sides, so they do not explain the between-side difference. Still, the small sample and the multi-ingredient composition make it impossible to establish an independent effect of carnitine [10].

Neither carnitine's role in energy metabolism nor a favorable rating of the cream confirms an independent lipolytic action.

Rejuvenation: credit the formula, not the carnitine

In a study by Czajka et al. (2018), a multi-ingredient supplement was reported to improve skin elasticity by 40% after 90 days. However, the product contained not only L-carnitine but also fish collagen, vitamins, and antioxidants. Carnitine's separate contribution was not established [11].

Another type of data comes from experiments on human mesenchymal stem cells outside the body. Farahzadi et al. (2016) examined the effect of L-carnitine on expression of the gene for the catalytic subunit of telomerase and on telomere length. Such findings help to study cellular mechanisms, but they do not mean a patient's skin has been rejuvenated and do not confirm that a cream or supplement works [12].

Role 2. Potential therapeutic support

The goal here is different: not to change the appearance of the skin but to reduce specific consequences of a disease or adverse effects of its main treatment. Research use of carnitine in dermatoses must be distinguished from the approved indications of levocarnitine medicines.

In pemphigus vulgaris, carnitine has been studied alongside corticosteroid therapy. Noormohammadi et al. (2023) assessed laboratory markers of muscle metabolism: insulin-like growth factor 1, creatine kinase, myostatin and myogenin. The authors found no between-group differences for any marker, and biomarker changes do not demonstrate preserved muscle mass and strength [13]. Another study looked at bone turnover markers, not fracture rates [14]. Presenting these studies as proof of preventing steroid myopathy or osteoporosis is therefore premature.

The review also includes work on reducing muscle symptoms with isotretinoin and vismodegib. Georgala et al. (1999) studied carnitine for muscle complaints during treatment of severe acne [15]. In a small pilot randomized trial, Cannon et al. (2018) assessed it for vismodegib-associated muscle spasms: of 12 enrolled patients, results could be evaluated in 8 [16]. Such data deserve further study but do not yet form a universal strategy for preventing adverse effects.

Tissue repair in vascular disease is a separate line. Pola et al. (1991), for example, studied propionyl-L-carnitine in 18 patients with chronic arterial, venous and mixed ulcers of the lower limbs [17]. That is a different clinical situation and a different carnitine derivative; the results cannot be automatically transferred to recovery after laser, injectable, or other aesthetic procedures.

Role 3. A biomarker candidate, not a ready diagnostic test

Carnitine's third role is not treatment but a reflection of metabolic features. In atopic dermatitis and psoriasis, differences in the carnitine profile of blood and skin have been described, and the findings depend on the disease and the material studied [18]. In systemic sclerosis, carnitine and fatty acid metabolism are dysregulated [19], and in keloids there are changes in circulating metabolites, including palmitoylcarnitine [20].

What is at issue is not a single universal measure, "carnitine level", but different molecules and their ratios. A higher concentration of one acylcarnitine and a lower concentration of another may reflect different metabolic processes. Blood test results and skin tissue findings therefore cannot be treated as interchangeable.

Such findings may help to understand pathogenesis, but they do not yet justify routine "carnitine screening". A lower concentration does not necessarily mean a cause of disease or a reason to take a supplement. Analysis of genetically predicted metabolite levels in acne is instructive too: nominal associations did not survive correction for multiple comparisons [21].

For a biomarker candidate to become a diagnostic tool, a difference between patients and healthy people is not enough. Reproducibility must be confirmed, along with clinical value — for example, the ability to refine diagnosis or prognosis beyond existing methods. The data presented do not yet establish such a use for the carnitine profile in everyday dermatology practice.

Safety without universal guarantees

Most of the studies reviewed reported no significant adverse events, but small samples and short follow-up limit such conclusions. For medicinal levocarnitine, gastrointestinal reactions, a distinctive body odor, hypersensitivity reactions, and reports of seizures have been described. Concomitant use with warfarin requires attention to the international normalized ratio (INR) [3]. The absence of marked reactions in a small study therefore does not mean an absence of risk in any given patient.

Another issue with systemic use is the formation of trimethylamine N-oxide (TMAO) via gut microbiota. In a study by Samulak et al. (2019), L-carnitine supplementation raised TMAO without a simultaneous worsening of the atherosclerosis markers studied [22]. This does not settle the question of long-term cardiovascular risk: the link between TMAO and cardiovascular disease and its causal interpretation remain under discussion [23].

Overall assessment is hampered by heterogeneity of doses, formulations and outcomes, by multi-ingredient interventions and by a lack of long-term data. Chow and Sapijaszko also note that Beiersdorf, the manufacturer of carnitine-containing products, funded many studies of topical products. That does not invalidate the results, but it matters for critical reading.

What remains for practice

For oily skin and acne, carnitine is worth discussing as a component of a specific skincare product. In the Detudom study, researchers assessed reduced sebum secretion at four weeks, but there was no group without active ingredients. In the How study, the advantage of the formula with carnitine and licochalcone A concerned tolerability of adapalene, not a greater reduction in acne lesion counts. The correct practical emphasis, then, is supporting therapy and controlling oiliness, not replacing acne treatment with a "carnitine cream".

After procedures and in post-acne pigmentation, carnitine in a sunscreen gives no grounds to promise prevention of hyperpigmentation. After the picosecond laser, the studied formula showed no significant advantage on this outcome. The positive IPL result relates to a different procedure and a different multi-ingredient formula.

For cellulite and age-related changes, reductions in body circumference or improvements in skin elasticity in complex products cannot be attributed to carnitine. It is especially important not to turn "elasticity improved by 40%" into an argument for L-carnitine itself: the study used a supplement with collagen and other ingredients. Cell culture data likewise do not justify prescribing carnitine to "lengthen telomeres" in a patient.

For muscle complaints during systemic therapy, the review gives grounds to discuss further study of carnitine, not its automatic prescription for everyone receiving isotretinoin, vismodegib, or corticosteroids. A supplement should not replace evaluation of symptom causes, necessary laboratory monitoring, or a decision about adjusting the main treatment.

In atopic dermatitis, psoriasis, and fibrosing conditions, the carnitine profile described remains a research finding. It establishes no indication either for routine testing or for taking a supplement. So the three roles of carnitine have different levels of practical readiness today: topical formulas have already been studied in clinical settings, systemic support needs its place in therapy defined, and biomarker use needs further clinical validation.

References

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