Kerassentials Ingredients: The Full Label, Ingredient by Ingredient

By Leah CorbinEditor, Kerassentials ReviewUpdated October 21, 20264 min read

Kerassentials lists 17 ingredients on its label. One is a named active at a stated strength, five are essential oils chosen for their antifungal properties, and the rest condition the skin and carry the formula into the nail. This page takes them in that order.

The label

Ingredients, as printed on the bottle in label order: undecylenic acid USP (5%), mineral oil, sweet almond oil, organic flaxseed oil, tea tree oil, aloe vera leaf extract, canola oil, tocopheryl acetate (vitamin E), walnut oil, menthol, camphor oil, clove bud oil, jojoba oil, chia oil, lemongrass oil, lavender oil and manuka oil.

The bottle holds 0.5 oz (15 ml). Directions are four applications a day with the brush, plus a cotton swab for the cuticle. The label also says to file the nail surface with an emery board so the oil can absorb.

The active: undecylenic acid (5%)

Undecylenic acid is a fatty acid made from castor oil. It has been used against fungal skin infections for decades and is one of the antifungal actives the FDA allows in over-the-counter athlete's foot and ringworm products. The federal rule, 21 CFR 333.210, sets the allowed strength for those products at 10 to 25% total undecylenate.

In the lab, undecylenic acid damages the fungal cell surface and stops Candida yeast from switching to the thread-like form it uses to invade tissue. A 2016 study found it blocked biofilm formation, the protective layer fungi build on surfaces. A Cochrane review of skin treatments found undecanoates beat placebo for athlete's foot.

Kerassentials uses it at 5%, below the athlete's foot range. Within this formula it is one active among several, working alongside the essential oils, which is a reasonable design for a daily nail oil.

Essential oils

Tea tree oil has the best clinical record of any natural nail fungus remedy. In a 1994 randomized trial, people with toenail fungus applied either 100% tea tree oil or 1% clotrimazole twice a day for six months. The two groups did about the same: 60% of the tea tree group had partial or full clinical resolution, and culture cure was 18% for tea tree against 11% for clotrimazole. A separate trial using a cream with 5% tea tree oil plus the drug butenafine cured 80% of patients after 16 weeks. The NCCIH tea tree oil page covers its safety.

Clove bud oil is mostly eugenol. A 2009 study in the Journal of Medical Microbiology found clove oil and eugenol killed Candida, Aspergillus and dermatophytes, including strains resistant to fluconazole, by breaking down the fungal membrane and cutting ergosterol production.

Manuka oil comes from the New Zealand tea tree, a cousin of the Australian plant. Lab studies find it at least as active as tea tree oil against some fungi.

Lemongrass oil contains citral, which in vapor and contact tests strongly inhibited Trichophyton, the main cause of toenail fungus.

Lavender oil is antifungal in lab work and calming on skin. It also gives the oil a pleasant smell, which helps when you are applying it four times a day.

A 2016 review of essential oils for onychomycosis concluded that these small, oily molecules are good candidates for nail treatment because they penetrate the nail plate, act on fungi in several ways at once, and rarely trigger resistance.

Menthol and camphor

Menthol and camphor are the cooling compounds in VapoRub, and that is not a coincidence. In a 2011 case series, 18 people with toenail fungus applied VapoRub daily for 48 weeks; 83% improved and about 28% were completely cleared. Researchers think the camphor, menthol and eucalyptus oil in it act on the fungus and help the ointment soak into the nail. Kerassentials includes the first two. They also explain the cool tingle when you apply it. More detail is in our note on VapoRub for toenail fungus.

Skin and cuticle conditioners

Aloe vera soothes irritated skin and has some antifungal activity of its own. Vitamin E (tocopheryl acetate) protects skin oils from breaking down; a vitamin E nail oil with tea tree, lime and oregano oils cleared 78.5% of mild to moderate cases in a 12-month open study published in 2020.

The carrier oils, sweet almond, flaxseed, jojoba, chia, walnut and canola, plus mineral oil, make up most of the bottle. They thin the essential oils to a skin-safe strength, spread the formula across the nail and into the cuticle, and soften the cracked, dry skin that usually comes with a fungal nail. Jojoba is especially close to the skin's own oils. Flaxseed and chia add omega-3 fats.

Note the almond and walnut oils if you have a tree nut allergy.

What isn't in it

There are no prescription antifungal drugs, no alcohol on the ingredient list and no added fragrance beyond the essential oils themselves. There is also no urea, the nail softener used in many drugstore gels. That makes Kerassentials gentler on the skin, but it means filing the nail, as the label suggests, does the job that urea would otherwise do for very thick nails.

One practical note on the label order: because essential oils are listed near the end, Kerassentials is much milder on the skin than undiluted tea tree or clove oil, which many people find too harsh to apply four times a day. The trade-off is a slower, steadier routine rather than a strong one-off dose.

How the formula compares

Most nail products on drugstore shelves take one of two roads: a single antifungal drug in a lacquer or cream, or a cosmetic gel that softens and smooths the nail without targeting fungus. Kerassentials sits between them, with a named antifungal active, several antifungal oils and a conditioning base. If you are weighing it against the best-known drugstore option, read Kerassentials vs Kerasal. For our score and verdict, go back to the full Kerassentials review.