UAUKO Toenail Fungus Treatment Pen, 25% Undecylenic Acid, Pack of 4

The built-in brush makes it easy to apply this nail treatment precisely around the cuticle and nail edges. Its formula contains 25% undecylenic acid alongside tea tree oil and other botanical ingredients. Use it on fingernails or toenails as part of a regular nail-care routine. The pack includes four 3 ml pens.

Tech summary

This extra-strength treatment is designed for nails affected by fungus beneath or around the nail, including concerns such as discolouration, brittleness and surface damage. Undecylenic acid is the featured active ingredient, at a concentration of 25%. The formula also includes tea tree, jojoba, lavender, peppermint, apricot kernel, camphor and bergamot oils, as well as vitamin E and urea.

The brush applicator helps direct the liquid to the nail edges and cuticle, rather than requiring a separate applicator. It is suitable for both fingernails and toenails, so the same pen format can be used in a nail-care routine for either. The treatment is intended to support a healthier-looking appearance as affected nail grows out, nail appearance can change gradually over time.

Tips for day-to-day use

Apply a thin layer to the affected nail area, along the edges and around the cuticle, using the brush. The directions recommend applying twice daily and allowing about five minutes for absorption. A warm-water soak can help soften the nail before application. If you choose to file, thin the nail gently and avoid damaging the nail bed.

The suggested routine is at least 8–10 weeks, with continued use for 3–6 months recommended as new nail grows in. Keeping application consistent makes the pen practical to incorporate into a morning and evening routine. For shoppers choosing an applicator style, the built-in brush offers a direct way to place treatment around the nail without handling a separate brush.

What you get

The pack contains four 3 ml treatment pens. Each pen has a brush applicator for applying the liquid around the nail and cuticle, making it easy to keep the treatment format together with your everyday nail-care supplies. The four-pen pack is suited to a routine that calls for regular, repeated applications over time.

Should you buy it?

It suits you if you want a brush-on nail treatment for both fingernails and toenails, with undecylenic acid and a blend of botanical oils in the formula. The precise applicator and straightforward twice-daily directions make it a practical fit for focused care around nail edges and cuticles. Choose this four-pen pack for a consistent routine aimed at supporting healthier-looking nails as they grow.