1. Retinoic acid and retinoids are derivatives of vitamin A. They play a major role in many organ development and different tissues metabolic processes. Skin is not the only thing retinoids affect, and therefore retinol and its derivatives should be treated with caution, even if applied only topically. Retinol and its derivatives could interact with the embryo's nervous system, which is why they are not recommended during pregnancy and breastfeeding. Most dermatologists would advise to stop using retinol when you're starting to plan a family!
2. Retinol is one of the most powerful and well-known cosmetic ingredients and one of the few capable of penetrating through cellular membranes directly into skin cells. Once retinol or its derivatives are inside the cells, they alter the expression of genes involved in cellular proliferation and differentiation, which means they are technically epigenetically active. Retinol is able to prevent both specific collagen-destroying enzyme activation and oxidative stress while also stimulating the regeneration of deep skin structure.
3. Retinoid molecules can absorb UV light acting as an SPF filter. Unfortunately, they also increase the skin’s sensitivity to UV radiation because they speed up the skin renewal very significantly. The risk of sun-induced dermatitis or pigmentation is very high with the use of retinol-containing products. Take extra care and use SPF if you're using retinol.
4. Retinyl acetate and Retinyl palmitate are considered to be the least effective topical retinoids, as well as Retinyl propionate which doesn’t demonstrate any difference from placebo in clinical trials. The most effective (and the most aggressive) ingredients are retinol itself and retinoic acid. Both of them demonstrate clinical improvement in fine lines and skin elasticity after a few weeks of treatment, but the recommended duration of treatment is only 3 months. Side effects, nevertheless, could be significant: skin dryness, high sensitivity and irritation, photosensitivity and redness can persist for weeks. Another effective form is Retinaldehyde, which is well tolerated and allows comfortable prolonged use on the face and neck area.
5. The duration of retinol (retinaldehyde, retinoic acid) treatment is a subject of debate. First noticeable effects of retinol are achieved in about 4 weeks of use. Sadly, side effects could manifest earlier than that and demotivate patients to prolong the treatment, although this is a rare case. To obtain maximum results dermatologists recommend using retinol-based skincare for 18-20 consecutive weeks. Longer use, however, can diminish the results, so one must be careful. The effect after 44 weeks of use is still significant but less pronounced, and the skin can become hypersensitive, dry, flaky and prone to redness. Retinol speeds up the process of epidermis renewal, same as AHAs and BHAs, such as glycolic acid, salicylic acid and others. The use of retinol and acids together is strongly advised against as it could be dangerous, the only exception being certain chemical peels — but these should only be applied by aesthetic professionals.