Dryness

Water content and barrier function, together.

Hyaluronic acid

Hyaluronic Acid

Holding many times its weight in water is a beaker result. The human trial we found compared it with a ceramide cream in 20 people with atopic dermatitis, and the two products did not differ.

Not establishedBarrier lipid

Ceramides

An ingredient class — not a single line on an ingredient list

In 39 children with atopic dermatitis randomised three ways, a ceramide barrier cream, another prescription cream and an over-the-counter petrolatum ointment did not differ, and the petrolatum was at least 47 times more cost-effective. Applying emollients to newborns to prevent eczema also failed in a Cochrane review.

Moderate evidenceBarrier lipid

Panthenol

In a three-week study of 23 people on deliberately damaged skin, the reduction in transepidermal water loss was larger than control (−168.36 vs −123.38 g/m²/h, P = .023). What that control was, the abstract does not say.

Moderate evidenceSoothing

Centella asiatica

Centella Asiatica Extract

In a split-face trial of 30 people after laser resurfacing, the side treated with Centella extract gel showed a lower erythema index (coefficient −0.03, P = .046) and better crusting and wound appearance in the first days. Skin biophysics, though, did not differ between the two sides.

Moderate evidenceHumectant

Glycerin

In a double-blind crossover study of 51 people with dry skin, the finished emollient reduced transepidermal water loss more than the vehicle and more than the vehicle plus glycerol. Moisturising is the work of a formula, not of one ingredient.

Not establishedHumectant

Collagen

The rule of thumb in the skin-penetration literature is 500 daltons. Collagen is hundreds of times larger. That applying it increases collagen in the dermis has not been established in people.

Clinical procedures related to this concern

Procedures are not listed alongside topical ingredients. They are not something you use at home.

In preparation.