Allantoin: A Widely Used Skin-Conditioning Ingredient, and What the Evidence Supports

Allantoin shows up on a lot of ingredient lists, usually described as soothing. It is also one of those ingredients whose reputation is bigger than its evidence. Here is what it is, what it has been tested for, and what that does and does not tell you about your skin.

What It Is

Allantoin is a compound found in comfrey root (Symphytum officinale)^[1]. In cosmetics it is classed as a skin-conditioning agent. The Cosmetic Ingredient Review expert panel noted its use in 1,376 products at concentrations up to 2%^[2].

Its Safety Record

The same panel judged the safety data sufficient to support its use in the product categories and concentrations reviewed^[2]. That is a safety conclusion and a good one, which is why allantoin is common in gentle formulas. It is not a statement that allantoin does anything dramatic, and that is worth keeping separate.

What Animal Studies Show

The best-known efficacy work is in rats. In a study of 60 rats with open wounds, a lotion with 5% allantoin applied for 14 days was compared with the lotion base and with no treatment. Tissue analysis suggested that allantoin regulated the inflammatory response and stimulated fibroblast growth and the building of the extracellular matrix, and the authors concluded it sped up the return of normal skin^[3]. That is a useful mechanism clue, but it was in rats, in open wounds, at 5%. It does not tell you what 0.5% does on intact facial skin.

When Pure Allantoin Was Compared With Comfrey

A Serbian study compared pure allantoin with a comfrey root extract standardized to allantoin content. In cell tests, pure allantoin mildly slowed cell growth at higher concentrations. In volunteers whose skin was artificially irritated, preparations with the comfrey extract showed better anti-irritant potential than pure allantoin, and creams did better than gels on hydration and redness. The authors concluded that comfrey's activity cannot be attributed only to allantoin^[1]. In other words, the plant extract did better than the single compound it is often reduced to.

Scar Gels: A Combination, Not a Verdict

Allantoin is one of three ingredients (with onion extract and heparin) in a branded scar gel. In a study of 61 women with cesarean scars, the patient-rated score improved by 14.2% in the treated group while it declined by 14.8% in untreated scars at six weeks. The observer-rated score showed no significant change^[4]. The comparison was treated against untreated scars, not against a placebo gel. In a separate trial on 45 post-burn scars, silicone gel and silicone sheeting did better than the onion, heparin and allantoin gel^[5]. Because there are three ingredients in the gel, none of this can be credited to allantoin alone.

How to Read an Allantoin Claim

• Safety and benefit are different questions. Allantoin has a good safety record, but evidence for a visible effect on healthy skin is thin.
• Check the claim's source. Many "allantoin" results come from rats, from open wounds, or from combination products.
• Look at where it sits in the ingredient list, which runs from highest to lowest concentration. Our guide to reading an INCI list explains how.
• Do not expect it to replace the basics: a humectant, a moisturizer and daily sunscreen do the heavy lifting.
• Patch test a new product, as with any ingredient.