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Background: Topical retinoic acid (RA) causes irritation of the skin. To prevent this side effect, natural precursors of RA have been proposed. The aim of the present study was to compare the local tolerance profiles of retinol (ROL), retinaldehyde (RAL) and RA. Methods: ROL, RAL and RA were studied using repeated insult patch tests for 14 days (n = 6). Similarly, RAL and RA were assessed in long-term clinical use for 44 weeks (n = 355). Clinical scoring on irritation, measurement of transepidermal water loss (barrier function) and laser Doppler blood flow perfusion units (irritation) were performed. Results: Under maximized conditions, an equally low irritation potential for ROL and RAL and a more pronounced irritant effect with RA could be demonstrated clinically (p < 0.05 in the intergroup analysis). Furthermore, RAL and RA induced more scaling than ROL (p < 0.05), and ROL and RA tended to induce more burning/pruritus than RAL (nonsignificant). The TEWL values were low with ROL and high with RAL and RA (nonsignificant, intergroup analysis). The laser Doppler measurements confirmed pro-irritating effects of RA and the nonirritating effects of ROL and RAL (p = 0.001, intergroup analysis). The long-term clinical study showed that the study population developed a high frequency of erythema (44% of the population), scaling (35%) and burning/pruritus (29%) with RA in the first 4 weeks of treatment, whereas these 3 parameters were significantly less frequent with RAL (p < 0.0001 in the intergroup analysis). Conclusion: The natural retinoids ROL and RAL do have a good tolerance profile, in contrast with the irritating potential of RA.

Background: The natural precursor of retinoic acid, i.e. retinaldehyde, has been proven to exert retinoid activities. Aim and Methods: The aim of this prospective instrument study was to determine the effect of topical retinaldehyde 0.05% on the physical properties of aging skin. This was performed using two devices, namely a high-resolution (70–80 µm) ultrasound scanner, which visualizes the thickness of both the epidermis and the dermis, and an echorheometer, which assesses the stiffness and elasticity of the skin by suction. In a 1-year study, 21 patients applied retinaldehyde cream 0.05% on the face, while another group of 19 volunteers were only treated with an emollient (control group). Epidermal and dermal thicknesses were measured on the forehead and temple, and stiffness and elasticity were measured on the forehead only. All the instrumental parameters were assessed at baseline and at the end of treatment. Results: Compared to the control group, retinaldehyde treatment induced a significant increase in epidermal thickness of the temple, as well as in cutaneous elasticity (p < 0.01). Similarly, retinaldehyde treatment tended to increase dermal thickness and reduce cutaneous stiffness, but no statistical difference could be observed between the two groups. Conclusion: Taken together, the results further suggest that retinaldehyde has counteracting effects on skin aging

Background: Anecdotal observations suggest that retinoic acid may be effective in mild rosacea. Aim: Our aim was to investigate, by an exploratory clinical and instrumental study, the effects of a topical formulation with the retinoic acid precursor retinaldehyde, in patients with vascular signs of facial rosacea. Methods: Female patients were treated with a 0.05% retinaldehyde cream that was applied once daily for 6 months. Clinical assessments of persistent erythema and telangiectasia were performed every month, using a 4-point severity score (absent to severe). The clinical response for each parameter was defined as a decrease of at least 1 grade in the severity score. In addition, erythema was further evaluated by measurement of the a* parameter, using a spectrophotometer on lesional and nonlesional areas. Results: A total of 23 women comprised the study population. At baseline, 10 patients had diffuse erythema, 3 patients had isolated telangiectasia and 10 patients had both. During retinaldehyde treatment, a clinical response was revealed in about 75% of the patients with erythema, after 5 months (p < 0.05). Similarly, isolated telangiectasia responded to retinaldehyde, although to a lesser extent and after a longer period of treatment (46% responders after 6 months, nonsignificant). Using the spectrophotometer, the a* parameter diminished in patients with erythema by about 15%, after 2 months of treatment (p = 0.001). Conclusion: This study indicates that retinaldehyde has beneficial effects on the vascular component of rosacea.

Background: Retinaldehyde (RAL), a key metabolite between vitamin A and retinoic acid, acts by modulating differentiation and proliferation of keratinocytes, which is of interest in acne lesions, mainly retentional lesions. Glycolic acid increases the exfoliation of corneocytes explaining its mild activity on retentional lesions. Thus, RAL and glycolic acid combined in the same product (Diacnéal^®) have complementary activities which can be of interest for acne patients. The aim of this study was to evaluate the tolerance of Diacnéal used by 1,709 acne patients in combination with their usual acne products except retinoids. Results: This study demonstrated a very good tolerance of Diacnéal when used with other acne treatments for 90 days. Complaints about side-effects were rare. Moreover, the significant decrease in both inflammatory and retentional lesions between day 0 and day 90 indicates that Diacnéal could amplify the efficiency of other anti-acne products used at the same time by the patients. The subjective evaluation of the preparation’s efficacy by investigators and patients was strongly favourable. Conclusion: These data show that a combination of RAL 0.1% and glycolic acid 6% may be used in association with other topical anti-acne treatments (benzoyl peroxide and topical antibiotics) with an excellent tolerance.