A mushroom with a long history

White, gelatinous and slightly translucent, Tremella fuciformis — also called white fungus, snow fungus or silver ear — grows on tree trunks in the damp forests of Asia. China has long known it in cooking — soups, desserts — and in some traditional uses. Its reputation comes from its texture: it holds a lot of water, and it absorbs plenty. That is how it ended up, without really asking, as the star of serums first popularised by Korean routines, then taken up by French brands as a plant-derived selling point, often organic.

In a bottle, tremella is rarely flying solo. It shares the formula with glycerin, propanediol and sometimes hyaluronic acid: these classic humectants do most of the hydrating work. That doesn't take anything away from tremella, but it does put things back in perspective. The mushroom is not some wonder ingredient from the forest floor. It is a comfort ingredient, with a good story and a pleasant texture.

Tremella and hyaluronic acid are not in competition

Both are humectants: they attract water and hold it at the surface. Hyaluronic acid has decades of use behind it, several molecule sizes and a well-stocked body of literature. Tremella brings polysaccharides and a reputation for a more fluid, less sticky texture. That last point is about how it feels in use, not a laboratory protocol: published comparisons remain limited.

So should you switch? If hyaluronic acid leaves your skin feeling tight, or if you want something lighter under your moisturiser, tremella makes a very good case for itself. If hyaluronic acid already suits you, there is no rush to change. A serum is not a belief system — and your skin, generally, just wants to be comfortable.

How to spot the active in the INCI list

Go straight to the label and the ingredients list. Look for Tremella fuciformis, often followed by 'extract'. In principle, the list runs in descending order of concentration: as a rule, that order is only really meaningful for ingredients present at more than 1%; those below 1% can be listed in any order. In practice, that means if the mushroom appears after the preservative (usually phenoxyethanol), there is no way of knowing whether it is present at 0.9% or 0.05%. And if it sits at the top of the list, be cautious in the other direction: some very marketable ingredients are mainly a marketing talking point.

One last check: the word 'natural' is not a certification. If a brand claims to be organic, look for Cosmos or Ecocert on the box — that is what actually guarantees something, not the adjective printed in large type.

The step that makes the difference: apply your serum to slightly damp skin, not dry skin. A humectant needs water to work; in a heated room, applied to thirsty skin, it can instead leave you feeling uncomfortable. Use a face mist or toner first, then two or three drops, then moisturiser on top to seal it in.

Packaging matters as much as the formula

Glass recycles better than plastic and protects the formula well, but it weighs down a travel bag. A refill, when a brand offers one, cuts packaging — as long as it is actually available, which is not always the case. A jar often contains more product, but fingers go in and the formula oxidises faster. A pump bottle limits contact, at the cost of a mechanism that is often plastic.

For your bag, a 10 to 15 ml travel size is enough. A real-life tip: try a small size first before investing in a large bottle. Textures that other people love are not always the ones you will love on your own skin, and a serum you never finish is not exactly eco-friendly.

Budget

In the UK, expect to pay roughly £15 to £40 for a tremella serum from a pharmacy, health-food shop or brand website, including French brands' own sites. The price varies with the size, the concentration of actives, the certification and whether a refill is available: a small, prettily packaged bottle can cost more than a large, plain one.

Always work out the price per millilitre. A 30 ml bottle at £25 is often better value than a 15 ml one at £35, provided the formula suits you. And remember that a hydrating serum does not need to be spectacular to be useful: it is a comfort product, not a bathroom trophy.