Three causes, one of them fixable

Plasticiser migration. TPE, TPR and soft PVC are made soft by adding oils and plasticisers. Those additives are not chemically bonded into the polymer — they sit inside it, held by nothing stronger than proximity. Over time they diffuse outward, reach the surface and evaporate. What you feel is the residue of that process sitting on a material that has lost some of what made it soft. Heat speeds it up, so does sunlight, so does body warmth, so does time.

This one is permanent. The oil is leaving the product; you cannot put it back. When a TPE toy goes tacky it has started a process with no reverse gear.

Low-molecular silicone oil on a silicone surface. Silicone lubricants contain dimethicones and cyclomethicones of varying chain length. The short ones can migrate into the surface layer of a silicone toy and make it feel greasy or tacky. The long ones mostly sit on top and wipe off. This is the reason for the blanket advice to keep silicone lube away from silicone toys, and the blanket advice overstates it: a high-viscosity silicone lubricant is a much smaller problem than a thin one, and the effect is a surface condition rather than structural damage. It can often be cleaned back.

Incomplete curing. Platinum-cure silicone has no plasticiser to lose — it is a cross-linked network, which is why it does not go tacky with age. But a lot of what is sold as silicone is silicone blended with TPE, or a cheap cure that never fully finished. Those behave like TPE, just with better marketing. If a toy arrived slightly tacky, or went sticky within weeks of normal use, suspect this rather than your cleaning routine.

Telling them apart

Wash it properly, dry it completely, then dust it lightly with cornstarch — not talc, which has its own history of contamination concerns — and leave it somewhere cool and dry for two days.

If it comes back tacky within that window, the oil is coming from inside the material. It is finished. Replace it.

If it stays dry, what you had was surface contamination: lubricant residue, something it was stored against, or a cleaner that left a film. That is cleanable, and the fix is the wash you just did plus not repeating whatever caused it.

Two days sounds like a long time to answer a simple question. It is the only test that distinguishes the two, because everything else — how it feels after washing, how it looks — is identical in both cases.

What cornstarch actually does

It absorbs the oil sitting on the surface, which restores the dry, matte feel for a while. It does not slow the migration, does not reach anything below the surface, and washes off the moment you use the toy again.

That makes it a reasonable thing to do before storing something, and a bad thing to rely on. If you are re-powdering every week, you are maintaining a symptom of a material that is on its way out. The powder is also mildly abrasive over time and dulls the surface texture — the thing you paid extra for on a soft toy.

When to stop trying

Replace it when any of these is true:

• The tack returns within two days of powdering.
• It still smells after washing and drying. Smell that survives a wash is coming from inside the material, not the surface.
• You can see fine cracks, especially where it flexes.
• It has gone hard or lost its give. Plasticiser loss and hardening are the same process at different stages.
• It is TPE and it is more than about a year old with regular use. Three to six months is a realistic life for a soft TPE toy that gets used often.

None of that is a reason to feel bad about the purchase. TPE is cheap to make, feels good when new, and is honest about nothing. The information that it is a consumable is simply not on the box.