What are the different modes of use for hyaluronic acid?

On the skin, hyaluronic acid is first used for its powerful moisturizing properties. Capable of holding up to 1,000 times its weight in water, it helps maintain proper hydration of the epidermis, strengthens the barrier function, and improves skin suppleness. Hyaluronic acid exists in different molecular weights. The high-molecular-weight form creates a protective film on the skin’s surface, while the low-molecular-weight form penetrates more deeply into the epidermis and helps reactivate cellular activity. Topical use of hyaluronic acid can thus improve skin radiance and smooth dehydration lines. Moreover, studies have shown that hyaluronic acid possesses anti-inflammatory, antioxidant, and healing properties, demonstrating its versatility.

The application of skincare products containing hyaluronic acid can be applied morning and evening, as this active ingredient is not photosensitizing. It is found in serums, creams, or lotions at concentrations varying but often between 0.01% and 3%. Hyaluronic acid can be used alone or in combination with other actives, such as vitamin C or niacinamide, which are also very popular in cosmetics. It has no particular contraindication and is well tolerated by all skin types, including the most sensitive. The hyaluronic acid is also compatible with skincare products containing retinoids or fruit acids, as an adjunct to help minimize irritation.

As for hair, scientific data are more limited, but the hyaluronic acid appears promising, particularly for enhancing hair fiber strength. On the scalp, its effects mirror those seen on the skin, where hyaluronic acid can soothe irritation and improve hydration and the skin barrier. The hyaluronic acid can be found in shampoos, conditioners, masks, or hair serums. Its mode of application then depends on the formula: some products require a specific application time, while others are formulated as leave-in treatments. It is recommended to follow the manufacturer’s instructions. Finally, it is useful to know that hyaluronic acid is regarded as an active ingredient suitable for all hair types, whether kinky, straight, curly, or dull.

The hyaluronic acid is also widely used in the field of aesthetic medicine. Unlike topical hyaluronic acid, injections can act deeply to fill pronounced wrinkles, restore facial volume, reshape contours, plump lips, or soften certain scars. However, these medical procedures are strictly contraindicated for pregnant or breastfeeding women, patients with autoimmune diseases, those undergoing anticoagulant therapy, or individuals with a skin infection. It is also recommended to avoid any sun exposure in the days preceding the session.

Did you know? Injected hyaluronic acid is typically cross-linked hyaluronic acid, a specialized form obtained by chemically bonding multiple chains with a cross-linking agent to create a dense three-dimensional structure that is less prone to degradation by the enzymes present in the skin.

Hyaluronic acid injections are performed using a blunt-tip cannula, directly into the dermis. The procedure, usually minimally painful, may produce a tingling sensation during the injection, which is alleviated by prior application of a local anesthetic. Depending on the area treated, the session lasts between 10 and 30 minutes. The results generally become visible between one and four weeks after the procedure and last on average between 6 and 24 months, depending on the gel’s density and the treatment location. Because of the inflammatory reaction induced by the injection, exposure to sunlight should be avoided for the week following treatment. Although adverse effects from hyaluronic acid injections are relatively rare, they should not be overlooked: redness, bruising, edema, and, in more severe cases, bacterial infections or localized necrosis can occur. Close medical follow-up helps prevent the majority of complications and ensures prompt management.

Oral hyaluronic acid supplementation is attracting growing interest, but its actual effects have yet to be confirmed.

Some studies suggest that a daily intake of hyaluronic acid may help improve skin hydration, skin elasticity, and even support joint function. A 2016 publication by OE and colleagues reviewed the existing scientific literature on this topic and concluded that oral hyaluronic acid could potentially emerge in the future as a valuable adjunct option for joint pain. This active compound may modulate inflammation by upregulating cytokine signaling-3 expression and downregulating pleiotrophin expression via the Toll-like receptor 4 in intestinal epithelial cells.

Studies on the effects of hyaluronic acid on the skin remain scarce and are often industry-funded, which warrants caution in interpreting the results. Moreover, once ingested, hyaluronic acid is fragmented in the digestive system, notably in the stomach and intestines. We then lack precise knowledge of where these fragments accumulate in the body. Nothing indicates that they preferentially migrate to the skin, a peripheral organ that the body does not treat as vital. Given the current state of knowledge, it is therefore premature to conclude that hyaluronic acid-based dietary supplements significantly improve skin hydration or elasticity.

Hyaluronic acid–based dietary supplements typically come as capsules or pills. Depending on the formulation, recommended doses range from 100 to 300 mg per day, sometimes combined with other active ingredients, such as collagen or zinc. Manufacturers often recommend a single daily intake, preferably with meals. Treatment duration varies according to the intended goals, but a period of 1 to 3 months is generally advised to observe any potential effects. To date, no adverse effects have been reported following oral hyaluronic acid supplementation, although it is generally not recommended for pregnant women as a precaution. Additionally, as with any dietary supplement, consulting a healthcare professional before beginning a regimen is advised, especially in cases of chronic illness or concurrent medication.

Hyaluronic acid is commonly used in rheumatology to relieve osteoarthritis-related pain, particularly in the knee. Naturally present in synovial fluid, it contributes to the lubrication and shock absorption of the joints. In osteoarthritis, its concentration and viscosity decrease, reducing cartilage protection and promoting painful joint friction. Intra-articular injection of hyaluronic acid, a procedure also known as viscosupplementation, aims to restore the viscoelastic properties of synovial fluid. Some studies have shown a moderate improvement in pain and mobility, especially in mild to moderate knee osteoarthritis. However, efficacy varies among individuals, and the observed benefits tend to diminish with the severity of joint damage. Moreover, relief is not immediate: it generally appears in the weeks following injection and lasts only a few months.

The hyaluronic acid used in this context is injected directly into the joint by a healthcare professional, most often under ultrasound guidance. One to three injections may be offered, spaced a week apart depending on the product. Although this procedure is minimally invasive, it is not risk-free. Local adverse effects can occur, such as transient pain, swelling, or joint inflammation. Infections are rare but possible. Hyaluronic acid injections are generally well tolerated and represent an appealing option when first-line treatments—such as analgesics or physical therapy—prove insufficient. However, they are not recommended in cases of joint infection or acute inflammatory flare-ups. Their efficacy in joints other than the knee, such as the hip, shoulder, or ankle, remains debated within the medical community.

Hyaluronic acid is also used in eye drops to relieve the symptoms of dry eye. Naturally present in the eye’s connective tissues, it retains water within them and contributes to the maintenance of ocular hydration and stabilization of the tear film. However, the eyes can still become dry when the naturally occurring hyaluronic acid is no longer sufficient to keep them lubricated. This can be due to certain autoimmune disorders, such as Sjögren’s syndrome, the use of medications like antihistamines or isotretinoin, an oral retinoid used to treat acne, as well as exposure to dry air, continuous contact lens wear, or prolonged screen time.

Hyaluronic acid–based eye drops are available over-the-counter and can be used multiple times a day, without any real restrictions, as needed. Their concentration generally ranges from 0.1% to 0.4%, with higher-concentration formulations often reserved for moderate to severe ocular dryness. Some products contain only hyaluronic acid, while others include complementary moisturizing and soothing agents, such as trehalose or allantoin.

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