Particularly valued for their hydrating and firming effects on the skin, peptides are found in many cosmetic products. Are you planning to start using peptides but concerned about their safety? We’re here to answer that question in this article.
Are there any potential risks associated with using peptides?
Summary
Published on April 5, 2022, updated on November 5, 2025, by Maylis, Chemical Engineer — 5 min of reading
Themes:
The essential points to remember.
Peptides are small proteins composed of chains of amino acids that are widely used in cosmetics.
Most peptides are well tolerated, even on sensitive skin, and pose virtually no risk of irritation.
Clinical studies, such as the one on peptide 14, have confirmed the safety of the peptides, with participants experiencing no skin reactions.
It is recommended, as with any cosmetic product, to perform a tolerance test before the first application, to prevent individual reactions.
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Why are peptides used in cosmetics?
The peptides are small proteins composed of chains of amino acids linked together by peptide bonds. Some amino acids are called essential, as the body cannot synthesize them and must obtain them via diet. The diversity of possible combinations enables the creation of molecules with a wide range of properties, capable of interacting with specific skin cells and enzymes, as well as hair follicles.
In cosmetics, the peptides are used for their multiple biological activities: some can stimulate the production of collagen and elastin, two fibrous proteins that give the dermis its suppleness and elasticity, while others have anti-inflammatory properties and promote skin healing. Others still, such as those derived from peas, target hair follicles to support the growth of hair, eyelashes, and eyebrows. In INCI lists, peptides are identified by prefixes that indicate their length: di-, tri-, tetra-, pentapeptides, and in various forms such as tetrapeptide-2, acetyl tetrapeptide-15, hexapeptide-2, or cyclopeptide-5.
What are the contraindications for peptides in cosmetics?
There are no contraindications to the topical use of skincare products containing peptides, and even pregnant and/or lactating women can use them.
Moreover, peptides are often identical or analogous to protein fragments already present in the body, which significantly reduces the risk of side effects. They are generally very well tolerated by all skin types, even the most sensitive, and the risk of allergic reaction is extremely low. The majority of peptides used in cosmetics have been tested in various clinical studies, and no serious reactions have been reported. Very rarely, isolated instances of redness have been observed, but these remain exceptional.
Several studies detail this safety, including one conducted with peptide 14, a peptide developed to modulate cellular senescence in the skin. Fibroblasts and keratinocytes were cultured for 24 hours in the presence of increasing concentrations of peptide 14 (0.01–100 μM). The results of the MTT cell viability assay showed that the peptide did not alter cell survival, even at the maximum concentration of 100 μM. For reference, this assay evaluates cell health by measuring the ability of cells to reduce the tetrazolium salt MTT into formazan, which is an indicator of their metabolic activity.
Results of MTT cell viability assays on fibroblasts and keratinocytes.
Source: CARVALHO J. L. & al. In vitro and in vivo toxicity assessment of the senotherapeutic Peptide 14. Toxicology Reports (2022).
The study also tested peptide 14 on human skin equivalents, following OECD 439 recommendations for reconstructed skin models. The results showed that no peptide concentration reduced skin tissue viability. On the contrary, all tested doses have slightly improved viability compared to untreated tissues. Qualitative histological analysis confirmed the integrity of the epidermis: the basal layer and epidermal stratification were preserved, with no alteration in epidermal thickness, which is a good indicator of skin tolerance.
Results of the MTT cell viability test on a human skin model.
Source: CARVALHO J. L. & al. In vitro and in vivo toxicity assessment of the senotherapeutic Peptide 14. Toxicology Reports (2022).
Finally, a patch test was performed on 54 participants aged 18 to 77 years, exposed to 1 mM of peptide 14 on the back under semi-occlusive conditions for a total of nine alternating applications over three weeks, followed by a final assessment on an untreated site ten days later. No participant exhibited any skin reaction, whether irritation, redness, swelling, or itching sensations, confirming the safety of peptide 14 even under repeated application conditions.
However, as with all skin care products, we still recommend performing a skin tolerance test before incorporating it into your routine. To do so, apply a small amount of the product in question to the inside of your elbow and wait 24 hours. If you observe any reaction, do not apply it to the rest of your skin or your hair.
Note : The diversity of peptides and their structures, however, makes it difficult to generalize their safety profile, as each molecule can behave differently depending on its composition and size.
Sources
LINTNER K. Peptides: What else? Cosmeticobs (2014).
ALMEIDA I. F. & al. Trending anti-aging peptides. Cosmetics (2020).
CARVALHO J. L. & al. In vitro and in vivo toxicity assessment of the senotherapeutic Peptide 14. Toxicology Reports (2022).
