Retinoids in Skin Care: A Complete Guide for Patients

Retinoids are compounds derived from vitamin A or its analogues. They act through retinoid receptors and alter the expression of certain genes involved in cell proliferation and differentiation.

Several molecules with different properties are used in dermatology.

Retinoid is the umbrella term for all derivatives in this class.

Tretinoin (retinoic acid) is the acidic, active form of vitamin A and does not require conversion in the skin. It is one of the most extensively studied topical retinoids for both acne and photoaging.

Adapalene is a third-generation synthetic retinoid used primarily to treat acne. It has comedolytic and anti-inflammatory properties and is generally well tolerated compared with some other topical retinoids.

Tazarotene is a potent topical retinoid used primarily for acne and certain keratinization disorders, including psoriasis.

Retinol and retinal (retinaldehyde) are forms found mainly in dermocosmetic products. They must be converted in the skin before becoming retinoic acid, the biologically active form. They generally have lower activity than tretinoin but may be more easily tolerated.

Isotretinoin is a powerful oral medication prescribed to treat severe forms of acne, such as nodular or conglobate acne, that are refractory to topical treatments.

It is therefore important not to use the terms “retinol,” “retinal,” “retinoid,” and “tretinoin” as though they were synonymous. They belong to the same family but are not equivalent in terms of structure, potency, indications, or medication status.

From acne to fine lines—what the studies show

Acne vulgaris. The effectiveness of topical retinoids in acne vulgaris has been extensively documented: they reduce existing comedones, prevent new ones from forming, and have a moderate anti-inflammatory effect. They are recommended as first-line or maintenance therapy in most clinical practice guidelines.

Photoaging. In photoaging, classic placebo-controlled studies have shown that long-term application of topical tretinoin visibly improves fine lines, pigmentation irregularities, and the overall appearance of skin texture by stimulating dermal collagen synthesis and reorganizing disordered elastic fibers.

Beyond acne and aging, retinoids also have consistent evidence supporting their use in improving post-inflammatory hyperpigmentation and the texture of skin with enlarged pores. It is important to emphasize to patients that visible results take time—generally 8–12 weeks of consistent use for acne and several months for anti-aging effects—in contrast to the promises of “instant results” frequently encountered in marketing.

The most common adverse reaction—redness, mild flaking, and a stinging sensation—is known as “retinization.” It usually occurs during the first 2–4 weeks and is a direct consequence of accelerated cell turnover. It is not a sign of allergy but a temporary adaptive response that subsides as the skin barrier adjusts to the new renewal rate.

The recommended approach to minimizing discomfort includes using a small amount (a pea-sized quantity for the entire face), introducing it gradually (2–3 applications per week during the first few weeks, followed by a gradual increase in frequency), applying it to completely dry skin (which reduces penetration and, consequently, irritation), and incorporating an emollient moisturizer applied either before or after the retinoid to support the skin barrier. Equally important, daily photoprotection with an SPF of at least 30 is necessary because skin treated with retinoids temporarily becomes more sensitive to UV radiation, and a lack of protection may partially reverse the anti-aging benefits achieved.

Retinoids and pregnancy

There is an important difference between topical and systemic retinoids.

Systemic retinoids, particularly isotretinoin, have a well-established teratogenic risk and are contraindicated during pregnancy. With topical retinoids, systemic absorption is much lower, and the available observational data have not demonstrated a clear increase in the risk of birth defects. Nevertheless, because data are limited and alternative treatments are available, it is still recommended that topical retinoids be avoided during pregnancy.

Therefore, if a patient discovers that she is pregnant while using a topical retinoid, treatment should be discontinued and the situation discussed with her physician, without automatically assuming that accidental exposure has caused a fetal effect.