Allantoin, an active accelerator for skin healing?

When the skin is damaged, following an injury or acne for instance, it responds by initiating several defence mechanisms to combat inflammation including healing. This complex process consists of four stages: haemostasis, inflammation, proliferation, and tissue resolution.

The first phase of haemostasis begins as soon as the wound appears, with a vascular constriction and the formation of a fibrin clot. The clot and the surrounding wound tissue release pro-inflammatory cytokines and growth factors, such as transforming growth factor (TGF)-β, platelet-derived growth factor (PDGF), fibroblast growth factor (FGF) and epidermal growth factor (EGF).

As soon as the bleeding is under control, a movement of inflammatory cells migrating into the wound (chemotaxis) is observed, promoting the inflammatory phase which is characterised by the infiltration of neutrophils, macrophages, and lymphocytes.

The proliferative phase typically follows and overlaps the inflammatory phase, characterised by a process of re-epithelialisation, which is the regeneration of the epidermis facilitated by the activation of keratinocytes, the constitutive cells of the epidermis. These cells are located at the periphery of the wound and will multiply and migrate towards the injury zone, interacting with the components of the extracellular matrix.

The final stage is tissue resolution characterised by the formation of new blood vessels (angiogenesis) such that the vascular density of the wound returns to normal.

For over 80 years, allantoin has been used in cosmetic and pharmaceutical preparations for therapeutic purposes. It has often been cited in literature for its numerous pharmacological properties : moisturising, soothing, keratolytic and wound healing booster. However, the mechanism of action of allantoin on the wound healing process is still not well understood. Let's explore the results of a scientific study together.

A study conducted in 2010 aimed to identify the healing profile induced by allantoin. For this purpose, allantoin was incorporated at 5% into an emulsion and the experiments in vivo were carried out on injured rats. The results obtained showed that in both the rats treated with the 5% allantoin lotion and the control group of rats, the healing phase proceeded well. However, for the group of rats treated with the allantoin lotion, this healing process occurred more rapidly.

Indeed, from the third day onwards, a reduction in inflammatory cells and an early deposit of collagen is observed. Collagen stimulates and recruits immune cells and fibroblasts, promoting wound healing. For the control group, collagen deposition appears from the seventh day and the reduction of inflammatory cells from the fourteenth day.

These results suggest that allantoin promotes the healing process. It is hypothesised that it modulates the inflammatory response by potentially inhibiting the chemotaxis of inflammatory cells at the wound site. The early deposition of collagen induced by allantoin suggests that it plays a role in fibroblastic proliferation and the synthesis of extracellular matrix, a major element in the structure and organisation of skin tissues during healing.

Typically, allantoin is used at a concentration of 2% and mixed with other substances in formulations, but here a concentration of 5% was used to measure the effectiveness of allantoin alone on the healing process. Although these results seem promising, it is difficult to conclude that allantoin accelerates skin healing. It would intervene during the inflammatory phase, but again it is difficult to assert with this study whether, in addition to a healing power, allantoin would possess anti-inflammatory properties. Further clinical studies need to be conducted to confirm its role in this biological process and its mechanism of action.

• SILVA-BARCELLOS N. M. & al. Profile of wound healing process induced by allantoin. Acta Cirúrgica Brasileira (2010).