A sticky lens exterior is often caused by one of two things: a chemical reaction with products like insect repellent or sunscreen, or age/heat/UV-related breakdown of the rubberized/plastic coating itself. If it’s the material degrading, it usually isn’t truly reversible with cleaning.

If there’s any chance it’s residue on the surface, you can try very gentle cleaning first, but be cautious and avoid harsh solvents that could damage finishes, markings, or seals. If the stickiness is coming from the material itself, the practical fix is usually replacement of the affected exterior parts rather than trying to restore them.

One community answer also warned that degrading polymer material may be something you shouldn’t handle excessively, so it’s sensible to minimize contact and wash your hands after handling it until you know what’s going on.

In short: try only mild cleaning if you suspect contamination; if the coating itself has gone tacky from age or heat, replacement is the safer long-term solution.